232 Transactions. — Zoology. 



would very soon be worn down. It looks like a mere rudiment. In one of 

 my specimens (both from the Brothers) this third cone was present, in the 

 other absent. The one in which it was absent was not, I think, an old 

 specimen ; its teeth are in good order and very little, if at all, worn. This 

 therefore cannot be a specific distinction. Drs. Giinther and Knox disagree 

 in the number of teeth assigned to each maxilla and palate, but this arises 

 from the fact that Dr. Knox considers several of them complex teeth, while 

 Dr. Gtinther counts each cone as a distmct tooth. Gilnther says there are 

 about eighteen teeth in each maxilla which Knox counts as six. I counted 

 sixteen in mine and thirteen on each palate. Of the latter the largest and 

 strongest were in the middle. The teeth of the maxilla press the food 

 between the parallel rows of teeth, maxillary and palatine, and enter the 

 groove between them. Thus the three sets of teeth are differently sharpened ; 

 the mandibular teeth have both inner and outer sides ground by the others, 

 while the maxillary are sharpened on their inner and the palatine on their 

 outer faces. The teeth in my specimens were thirteen in the palate, of 

 which the anterior were very small. In the mandible nineteen, a canine and 

 incisors, two in number, and confluent at the bas"-. The teeth in mandible 

 and maxilla near the incisors are very small, and are soon worn away or 

 ground very small. In the other specimen was an additional incisor. 



The muscles which move the lower jaw are very short, thick, and 

 powerful. The crushing force of the jaws is very great. 



The tongue is thick and rough, the glottis a long narrow slit, with 

 closely-meeting raised edges. On forcibly opening the mouth of a living 

 specimen the tonsils appear very large. 



The posterior nares, two slits in the roof of the mouth, are situated just 

 inside the maxillary teeth at the junction of maxillary and premaxillary 

 bones. 



Thorax, Abdomen, and Pelvis. 



This large cavity is not divided by a diaphragm, though a portion of the 

 peritoneum is attached to the ribs where a diaphragm might be expected. 

 The peritoneum is a delicate membrane, in some parts colourless and trans- 

 parent, in others darker. The peritoneum is almost black in and near the 

 pelvis, but in many parts is much lighter, in some being of a greenish- 

 brown tint. The peritoneum lines the whole of the trunk cavity, and gives 

 off various large processes which attach the different organs to the spine ; 

 of these the largest are those which attach the rows of eggs to the spine. 

 The processes attached to the oviducts are black, but the mysentery is 

 transparent. The processes are half-an-inch in breadth, allowmg the rows 

 of eggs to rest on the abdominal walls. In the mysentery are long grey 

 bodies, corpora adiposa, 



