Putnam.] 156 [Nov. 19' 



Notes on the Genus Bdellostoma. By F. W. Putnam. 



Since making the remarks on Myxine, at the last meeting of the 

 Society, Professor Agassiz has very kindly placed at my disposal the 

 specimens of the allied genus Bdellostoma, which were obtained by 

 the Hassler Expedition at Talcahuano, Chili, about the middle of 

 April, 1872. 



These specimens were captured by the same means used by Profes- 

 sor Agassiz in collecting Myxine in the Straits of Magellan, showing 

 that the habits of the two genera are very similar. There are about 

 two hundred specimens in the lot, and all of nearly the same size. 

 The smallest one is thirteen inches in length, and is a female with 

 minute eggs ; the other specimens are about twenty inches in length. 



The general shape and anatomy of Bdellostoma is the same as that 

 of Myxine, as will be seen by the specimens and dissections on the 

 table. The cartilages of the head are more developed, so that the 

 parts composing the singular cartilaginous framework can be better 

 made out. There is also a slight difference in the ovary and in the 

 peritoneal outlet, and a modification of the branchial apparatus. 



The difference in the branchial apparatus of the two genera is at 

 first sight apparently greater than is really the case when the struc- 

 tures are compared. In Myxine there are six branchial sacs on each 

 side, each sac having a direct communication through its inner wall 

 with the oesophagus, from which it receives water, the water being 

 passed out by a duct leading from each sac to the single external 

 opening on the side of the abdominal line ; each lateral series of sacs 

 sending ducts to the external opening on its respective side.. 



In Bdellostoma cirrkatum, from the Cape of Good Hope and New 

 Zealand, which is the species so admirably dissected by Miiller, there 

 are either six or seven sacs on each side which receive water directly 

 from the oesophagus, as in Myxine, but the emptying ducts, instead of 

 passing backward and downward to a common external opening, as in 

 Myxine, pass directly through the wall of the body, and thus there are 

 as many external openings opposite the gill sacs on each side as there 

 are sacs. In Bdellostoma polytrema, the species to which the speci- 

 mens from Chili belong, there are ten sacs on each side, and each sac 

 opens directly through the walls of the body as in B. cirrhatum. So 

 that in this character the only difference betAveen Myxine and Bdel- 

 lostoma is, that the ducts in the former are elongated, all on one side 

 leading to the same opening, while in the latter they are short and 

 pass directly through the body wall, each for itself. 



