118 Transactions. — Zoology. 



its head a perfect ring, is not separable from its spiue. Each 

 soft fin ray can be spht into two halves after boiling. In the 

 cleft of the head is a nodule (divisible into two by careful 

 maceration) effecting the connection between the head of the 

 fin ray and the interspinous bone, and lying on the sloping 

 head of the latter behind the head of the predecessor. These 

 nodules are therefore a second (distal) series of pterygiophores, 

 and are probably homologous with the processes (of the inter- 

 spinous bones) entering the rings of the dorsal spines. 



The anal or ventral fin has elements similar to those of the 

 soft part of the dorsal. 



C. Alimentary Canal and Viscera. 



The short gullet leads into a straight, narrow, rugous 

 stomach. The U-shaped duodenum, wider than the stomach, 

 receives the bile-duct near its proximal end ; there are neither 

 pyloric coeca nor pancreas. The ileum, of three turns, is 

 separated from the rectum by an ileorectal valve. Of internal 

 parasites, Echinorhynchus occurs ofteuest. A species of Tetra- 

 rhynchus was found in all parts of the walls of the enteric 

 canal, ai:id also attached to these and to the mesenteries ; two 

 were found in the oviduct. A few specimens of a Nematode 

 were also found. The food consists mainly of Crustacea, espe- 

 cially crabs ; also univalves, mixed with a few leaves of Zostera. 

 This and the slimy nature of the skin befit the character of a 

 ground-feeder. 



The liver is mainly a three-sided prism, with a corner in 

 front bent over to represent a second lobe. The longitudinal 

 bile-duct lies in the gastrohepatic omentum, and receives seven 

 hepatic ducts in three sets, while its anterior end is continued 

 as the cystic duct to the gall-bladder. The spleen is a dark 

 reddish-brown ovoid body marked with black pigment-spots. 



Be2Jroductive Organs. — The testes, during the spawning- 

 season, are large, lobulated, and of whitish colour; and the 

 ovaries are very large and highly coloured. The single capa- 

 cious oviduct has flabby walls ; it is strengthened by an antero- 

 posterior band crossing its cavity. 



The well-developed swim-bladder consists of two chambers, 

 anterior and posterior, incompletely separated by a transverse 

 septum, which is perforated by a small circular aperture, and 

 which bears a number of small pink spots — retia mirabilia. 

 The large anterior chamber, unlike the posterior, is lined by a 

 silvery tissue ; and its anterior end is simply rounded off, 

 without any connection with the auditory organs, being sepa- 

 rated from the cranium by the degenerated pronephros — a 

 very vascular lymphoid body. The mesonephros is repre- 

 sented by a pair of thin dark bands, of which the right is 

 much the larger. The functional kidney is closely embedded 



