1873.] 129 [Putnam. 



from the oesophagus into each sac ; it is then passed out by a duct, 1 

 which continues backwards along the outer walls of the sacs to the 

 abdominal wall at the end of the last sac, where all the ducts from 

 one side unite in one, 2 and the water is emptied at the branchial 

 opening on each side of the median line. In close connection with 

 the branchial opening on the left side, there is a third opening 3 

 that leads by a very short duct to the oesophagus, and may be the 

 means of allowing water to pass directly into the oesophagus, and 

 hence into the branchial sacs, at times when the supply through 

 the mouth is cut off by the head being buried in the food of the 

 animal. The kidneys are long tubes situated on the median line 

 of the dorsal part of the abdominal cavity. The ovary is single 

 and is situated cm the right side of the intestinal canal. In 

 specimens where the ovary is not developed, it is seen as a simple 

 white membrane lying on the outer wall of the whole length of 

 the intestine, in close connection with the great mesenteric vein, 

 which is unusually large. As the eggs are developed the ovary is 

 stretched out, the eggs forming a fringe at its free edge. There are* 

 no oviducts; the eggs when mature break from their ovarian cap- 

 sules, and falling into the abdominal cavity are excluded through 

 the peritoneal opening at the side of the anal opening. 



With this hasty description of the general anatomy of the fishes 

 before us, I will proceed to the special subject of my communication, 

 which is to show that though the geographical distribution of the 

 croup is very extended, we can recognize but a single species in the 

 genus. 



The material which I have been able to use for this purpose is 

 quite extensive, an 1 consists of a fresh specimen dredged by Messrs. 

 Packard and Cooke off our eastern coast in September last, and sev- 

 eral specimens in the Museum of the Peabody Academy of Science, 

 which were presented by Prof. Agassiz to the Essex Institute in 1858, 

 and were collected at Grand Menan by Mr. J. C. Mills, during the 



1 The figure given by Home, and copied by Owen and other authors, does not cor- 

 rectly show the course of these branchial ducts, as they are represented a? short 

 ducts leading directly into one long tube that passes along the outer walls of the 

 sacs to the branchial opening. 



2 Midler's figure represents the ducts as here described. 



3 The figure mentioned in the preceding foot note represents the oesophagal open- 

 ing as somewhat removed from the left branchial opening, but in all the specimens 

 which I have examined its position is so close to the left branchial opening as to 

 form one cavity with it. 



PROCEEDINGS B. S. K. E. — VOL. XVI. 9 FEBRUARY, 1871. 



