60 MR. NELSON ANNANUALE ON [Feb. 7, 



parasplienoid, extending along nearly the whole length of the 

 cranium. The auditory capsules had fused with the cranium and 

 were well-developed, although there was no external tympanic 

 membrane visible. The orbital arches were not formed, but the 

 structui'es connected with the gills had entirely disappeared. The 

 dorsal surface of the cranium is divided longitudinally by a simple 

 suture, which expands behind into a wedge-shaped cleft. 



The first seven vertebrae ai'e normal in structure and, with the 

 exception of the neural spine, thoroughly ossified ; those of the 

 tail are impei-fectly ossified and retain their identity. The eighth 

 and ninth vertebrae are abnormal ; they are fused together, the 

 anchylosis being complete on the dorsal surface but incomplete on 

 the sides and below. The doi-sal surface is nearly flat, but a slight 

 ridge can be detected running along the mid-dorsal line, and there 

 is a small mound-like elevation towards the left side on the eighth 

 vertebra. The transverse and articular processes are deformed 

 and asvm metrical in a manner and to a degree best shown in 

 Pl.VLfigs. le, 1/, Ir/. 



On the right side the only trace of the pelvic arch that can be 

 distinguished is a minute, irregularly-shaped fragment of bone 

 imbedded in a. broad ligament which is attached at one end to the 

 light transverse process of the ninth vertebra and ends in the 

 muscles of the body-wall at the other. On the left side, in the 

 coi'responding position, there is a sac lined with connective tissue 

 in the body- wall ; it does not communicate either with the 

 exterior or with the body-cavity. Its shape is an elongated oval, 

 sloping from near the doi'sal suiface forwards and downwards 

 towards the belly in front of the vent. A hernia, not strangulated 

 but containing a portion of the intestine, projects into it in front. 



Lying in this sac, but terminating above and below in the body- 

 wall, is a sickle- shaped bone, which appears to have been provided 

 with muscles not continuous with those of the body-wall. Un- 

 fortunately they are much decomposed. The bone is only fixed 

 to the walls of the sac by adhesions of connective tissue. Above it 

 is attached to the left ti'ansverse process of the ninth vertebra by 

 a ligament resembling that on the right side. It slopes downwards, 

 forwards and inwards, terminating in an expansion lodged in the 

 muscles of the belly just in front of the vent, which has a mesial 

 position. Its curve is slight, as is shown in fig. Ij, which 

 represents it as seen from in front when held vertically ; fig. 1 h 

 gives a view of the inner surface when the bone is lying in a 

 horizontal position. The relationship between it and the eighth 

 and ninth vertebi'Pe is accurately i-epresented in fig. If, but the 

 ligament has been omitted. 



Considering the form and relationships of this bone, there can 

 be no doubt that it i-epresents the left ilium, though its position 

 and forward slope are abnormal. The ligament which attaches it 

 to the vertebra must represent not only its own head but also the 

 distal extremity of the transverse process. The fragment of bone 

 and the ligament on the other side of the body similarly represent 



