600 DR. A. GUNTHER ON THE FISHES OF PANAMA. [^ ec - 13, 



intra-uterine formation it would seem as if the parts had been evolved 

 in a normal manner, and that only at the period when the external 

 genitals came to be developed did a departure from the female struc- 

 ture take place. Instead of the clitoris remaining in size and posi- 

 tion comparatively stationary, it increased as would a male organ, 

 but without becoming fully developed into a true penis ; while the 

 primary common genital cleft uniting, produced the lengthened pe- 

 rineal raphe. 



If this view be the correct one, it adds one more instance to sup- 

 port the opinion which some hold, that between the development 

 of the internal and external genitalia there is a certain amount of 

 independence ; for in the above example the inner organs would 

 have been necessarily more or less completely formed before devia- 

 tion from female sexual character occurred. 



Dr. A. Giinther read a memoir on the Fishes of the States of 

 Central America, founded upon specimens collected in the fresh and 

 marine waters of various parts of that country by Messrs. Salvin 

 and Godman and Capt. J. M. Dow. The specimens collected, 

 together with a few previously known from the same region, but not 

 contained in this collection, were referred to nearly 300 species. 



Dr. Giinther called particular attention to the fact that no less 

 than 48 of the marine species, out of a total of 158, from the seas on 

 both sides of the Isthmus of Panama were found to be identical, and 

 stated that this was to be explained only by assuming that, at a former 

 period, one or more open channels existed between the Atlantic and 

 Pacific. He added that, although a long time must have elapsed 

 since this communication was stopped, the specimens examined from 

 opposite coasts of the isthmus were absolutely identical, and that 

 there was no indication that any of these forms had undergone modi- 

 fication or degenerated into a climatic or local variety. 



After having defined the zoological characters of Central America, 

 as expressed in its fish-fauna, and subdivided it into six provinces, 

 he proceeded to give full descriptions of the new forms collected by 

 the gentlemen mentioned. Diagnoses of a part of these had been 

 already given in the 'Proceedings' of the Society, 1864, p. 144. 

 The following had not been mentioned before : — 



Plectropoma mtjltiguttatum. 



D.ii. A.i L.lat. 75. 



Allied to P. monacanthus. Prseoperculum with two spinous teeth 

 below the angle. 

 Panama. 



CORVINA CHRYSOLEUCA. 



Allied to C. ronchus. Second dorsal spine the strongest, third the 



