A PEELIMINARY NOTE ON THE FISHES OF LAKE BIWA. l3l 



length of the head less than it, making them thus approach more to the 

 vulgaris type. 



Similar states of things were observed by myself in many other 

 specimens of Anguilla in the collection of the Imperial Museum, and I 

 am rather inclined to think that the two species — vulgaris and hostonien- 

 sis — are the variaties of one and the same species. But as I have no 

 opportunity to look up the original descriptions of both the species, and 

 as their type-specimens are not found in any collections here in Tokyo, 

 the above statement is only to be looked upon, as a provisional suggestion 

 to be verified on a future occasion. It will, however, be of some 

 interest to notice that there exists a considerable fluctuation in the 

 proportional length of the head and the distance between the com- 

 mencements of the dorsal and the anal fins among the individuals of one 

 and the same species. This character, therefore, can not be of any 

 great value in the determination of the species of Anguilla. 



28. Petromyzon sp. (?). 



Jap. name : Yatsumeunagi. Loc. Nagahama. 



I caught twelve specimens of this Petromyzon in a small brook 

 running into the lake on the south side of the town Nagahama, three of 

 which proved to be females and nine, males. They were aggregated in 

 masses on the sandy bottom, their heads against the stream, and were 

 probably laying eggs. 



They are small animals, the largest female measuring 123 mm. in 

 length and the largest male only 118 mm., but the conditions of the eye 

 and the mouth show the adult structures of Petromyzon. They differ 

 both from P. fluviatidis and P. branchialis very markedly in having 

 higher dorsal fins, but resembles the- latter species in its dentition. 



To this list I may add three following fishes not collected by myself 

 in the present trip to the lake, but found among the specimens kept in 



