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XIV.—On a New Species of Sclerocheilus, with a Revision of the Genus

Published online by Cambridge University Press:  06 July 2012

J. H. Ashworth
J. H. Ashworth
Affiliation:
Lecturer in Invertebrate Zoology in the University of Edinburgh
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Extract

The Polychæte family Scalibregmidæ comprises seven genera, the limits and interrelationships of which are, however, still imperfectly known. The present paper results from a detailed study of one of these genera, a new species of which is described, chiefly from a specimen collected in Scotia Bay, South Orkneys, and entrusted to me for examination by Dr W. S. Bruce.

Description of the Specimen Collected in Scotia Bay, South Orkneys.: This specimen, the only Scalibregmid found by the Scottish National Antarctic Expedition, was dredged on a stony bottom in ten fathoms at Station 325, in Scotia Bay, South Orkneys (lat. 60° 43′ 42″ S.; long. 44° 38′ 33″ W.), in August 1903.

The worm, which is yellowish brown in colour (in alcohol), is 19 mm. long. The anterior portion is broad; the maximum breadth, 3 mm., is reached about the level of the 10th segment; from this region the worm tapers gradually to the anal segment. The dorsal surface of the worm is strongly convex; the ventral surface is flattened, and there is a well-marked depression which extends along the mid-ventral line from the 2nd chætiferous segment almost to the anus.

Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 50 , Issue 2 , 1915 , pp. 405 - 422
Copyright
Copyright © Royal Society of Edinburgh 1915

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References

page 406 note * This subdivision of the annuli is feebly marked on the ventral surface.

page 409 note * See the classification suggested by the writer in Quart. Journ. Micr. Sci., vol. xlv (1901), pp. 296, 297.

page 409 note † I have examined about sixty specimens of Scalibregma varying in length from 4 mm. to 56 mm., and including five epitokous examples. Eyes are present in only two specimens, both ordinary non-epitokous forms. For one of these specimens, which has been in my possession twelve years, I am indebted to Dr E. J. Allen, F.R.S., who collected it near Plymouth; for the other, collected in 1911 at Cap Lèvi, near Cherbourg, I have to thank Professor Fauvel, who, on finding that this specimen possessed eyes, kindly sent it to me for examination. Both specimens are similar in size, but only one—the Plymouth specimen—is complete; it is 30 mm. in length. In both, the eyes are on the right and left sides of the prostomium, and are wide apart, i.e. do not approach each other like those of Sclerocheilus. I have stained and cleared the Plymouth specimen, which exhibits on each side two eyes adjacent to each other, composed of a series of closely associated simple eyes, which in section are found to be similar in structure to those of Sclerocheilus.

page 409 note ‡ See Quart. Journ. Micr. Sci., vol. xlv (1901), pp. 291, 292.

page 409 note § The genus Lipobranchius founded by Messrs Cunningham and Ramage to contain the species L. jeffreysii (= Eumenia jeffreysii M'Intosh) cannot well contain also L. intermedius Saint-Joseph, which differs from the former in several respects, but especially in the nature of the chætæ of the first and second notopodia. A thorough revision of the genera Lipobranchius and Enmenia is required, and the relationship of L. jeffreysii to E. crassa should be reinvestigated. I have collected considerable material in view of undertaking such revision, but until I have the opportunity of examining certain types, which have been imperfectly described, the work is necessarily at a standstill.

page 410 note * Ann. Sci. Nat. Zool., vii sér., tome xvii (1894), p. 104 et seq.

page 410 note † For an account of the structure of the eyes, see A., et Dehorne, L., Arch. Zool. Expér., tome liii (1913), pp. 85–90.Google Scholar

page 411 note * Not more than about ·04 mm.

page 413 note * In a neuropodium from one of the specimens from Blacksod Bay, Co. Mayo, Ireland, there occurs a furcate chæta with an additional (third) prong, arising from between the bases of the two normal ones. This prong is shorter than either of the normal ones, the lengths being—normal prongs, 45μ and 27μ respectively; additional prong, 18μ.

page 413 note † Arch. f. Naturg., Jahrg. xxix, Bd. i (1863), Taf. v, fig. 3.

page 413 note ‡ 46 Jahresber. Schles. Ges. (1868), 1869, p. 67.

page 414 note * Since this was written the sense-organs have been briefly described by M., and Dehorne, Mme. in Arch. Zool. Expér., tome liii (1913), p. 72.Google Scholar

page 415 note * Proc. Acad. Nat. Sci. Philadelphia, 1909, p. 282.

page 415 note † The specimen has 62 chætiferous segments.

page 415 note ‡ Which are approximately round or oval in O. dicranochætus, and irregularly triangular in S. pacificus.

page 415 note § C. R. Acad. Sci. Paris, tome ci (1885), p. 1511.

page 415 note ║ See above, p. 409.

page 415 note ¶ Deuxième Expéd. Antarct. Franç.: Annélides Polychètes, 1911, p. 112.

page 416 note * Assuming, as is apparently the case, that there are no segments missing between the anterior and posterior portions into which the specimen is now divided.

page 417 note * Zool. Jahrb., Suppl. v (1901), p. 265. A fuller description of the specimen (collected at Tumbes, Chile) was given by ProfessorEhlers, in Festschr. K. Ges. Wiss. Göttingen, 1901, pp. 181, 182.Google Scholar

page 417 note † Abhandl. K. Ges. Wiss. Göttingen, Math.-Phys. Kl., N.F., Bd. iii, No. 1 (1904), p. 51; National Antarctic Exped., Nat. Hist., vol. vi (1912), p. 26; Deutsche Südpolar Exped., 1901–1903, Bd. xiii, Zool., v (1913), pp. 537, 538.

page 418 note * Bull. Mus. Comp. Zool. Harvard, vol. xliii (1906), p. 159.

page 418 note † The external features only are considered; there is not sufficient material of S. antarcticus to enable me to furnish a description of the internal organs, or to state if any of these may be employed as generic characters.

page 418 note ‡ σκληρός, hard; χεῖλος, lip. A name derived from the same roots, but spelt slightly differently—Sclerochilus— was employed soon afterwards by G. O. Sars to designate a new genus of Ostracods of the family Cytheridæ. See Forhandl. Vidensk.-Selsk. Christiania (1865), 1866, p. 89.

page 420 note * It will be observed that there is no record of the species from any point in the North Sea.