A character of the suture-line that has received considerable attention lately is the obliquity with regard to the radius. Of course, it had long been noticed that suture-lines may vary in the form and foliation of their elements (brachyphyllic, dolichophyllic, and leptophyllic suture-lines of Mojsisovics, and euryphyllian and stenophyllian suture-lines of Haug) as in their general course. There maybe (externally) a strong convexity forward (Cyclololus), a straight (Sphenodiscus) or wavy line (Pseudosageceras), or a convexity backward (Protengonoceras). Again, the suture-line may be inclined strongly forward towards the umbilicus (Cheltonia) or have a retracted or dependent inner portion (Psiloceras). It is this Litter obliquity that has been used as a generic and even family distinction, e.g. by Mr. Buckman, to determine the affinity of Bredya with Hammatoceratidse, and not Hildoceratidæ.