648 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Sidera castanea is very common among the rocks about Mazatlan, 

 where it reaches the length of about 4 feet, aucl is known to fishermen 

 as Anguila prieta. It has not yet been observed elsewhere. The types 

 numbered 28246, 29535, 29591, were collected by Mr. Gilbert. 



Indiana University, November 27, 1882. 



ON THE JVOiTIE!VCt.ATUKE OF THE GENUS OPHICHTHVS. 

 BY DAVID S. JORDAN AND CHARLES H. GILBERT. 



The generic name " Ophichthys Ahl" has been adopted by Dr. Giinther 

 for a large group of eels, including numerous nominal " genera " of earlier 

 writers. Whether this vast group will admit of further generic sub- 

 division, we do not here propose to discuss. It is, in any event, divis- 

 ible into subgenera, and for these subordinate grou^is we should adopt 

 names in accordance with accepted rules of nomenclature. It becomes, 

 tberefore, important to ascertain what species should be taken as the 

 type of Ophichthys. 



As the original memoir of Ahl is not, as far as we know, in any Ameri- 

 can library, we have written to Dr. Liitken, of the University of Copen- 

 hagen, in regard to it. His answer to this letter is the source of the 

 information given below in regard to the memoir in question. The fol- 

 lowing is the title: 



z.x.ar.^. 



Specimen ichthyologicum de Murwna et Ophichtho quod seria exp. fac. 

 med. Ups. priBsid. Carol. Vet. Thunherg. ccquite, etc. 



Modeste ofl'ert. 



Jonas Nicol. Ahl. 27 Jan. 1789. Upsalia. 



The genus Murccna is in this paper divided into two, as follows : 

 JTurwna. Ophichthus. 



"Animal apodum, pinnis ventra- "Animal apodum, ijinnis ventra- 



libus pectoralibus nullis. Mem- libus nullis; membrana branchios- 



brana branchiostigalO-radiata con- tiga 10-radiata connata. Apertnra 



nata. Apertnra branchiarum re- branchiarum remota lateralis ante- 



mota lateralis solitario." pinnis pectoralis. 



