CHONDEOSTOMA KNEEII. 203 



of the height. The base is shorter than that of the dorsal. The pectoral 

 fins are pointed, and quite as long as the head. The shorter ventral fins are 

 under the dorsal, and behind the middle of the body. The longest rays of 

 the caudal exceed the length of the head. The lateral line descends somewhat 

 concavely over the ventral fin. 



The scales are marked with wavy concentric striping, with an indefinite spot 

 in the middle. The free margin of a scale shows a fan 

 of twelve to fourteen rays. The largest scales are 

 two-thirds of the diameter of the eye. There are 

 five rows of scales between the lateral line and 

 ventral fin. 



The pectinate accessory gills are rather large. Fi S- 113. HEAD OF 



DROSTOMA KNERII (HECKEL), 



The cephalic canals are wide, and well developed. SEEN FROM BELOW. 

 The anterior gab-orbital branch can be traced by the 



sub-orbital bone to the end of the nose. It is very wide, and the canal 

 opens by two or three pores. The inner mucus skin of the mouth forms 

 numerous compact folds on the palate as in all other species of the genus, 

 but the margins of the mouth in this species look as though finely toothed, 

 for the parallel free edges of the furrows and folds of the skin of the palate 

 terminate laterally in a serration. 



The colour of the back is a brown or greenish-black. It becomes silvery 

 towards the abdomen, and in the anterior half of the body the scales are 

 covered with black pigment spots both on their free edge and at the base 

 behind the ventral fins. These spots are found only on the scales which lie 

 nearest to the lateral line. Before the tail terminates they cover the entire 

 height of the scales. 



Ckonclrostoma meigii (Steindachner), from Spain, is closely allied to this 

 fish, if it is not a variety of it. The pectoral fins are shorter. Its mouth is 

 described as semi-circular, and figured as transversely straight ; and we agree 

 with Dr. Giinther in hesitating to regard it as a distinct species until it has 

 been more fully described, though the more pointed form of head, more arched 

 back, and transverse mouth, render its specific difference probable. 



Chondrostoma rysela (AGASSIZ). 



D. 1112, A. 1213. Scales: lat. line 5060. transverse ^-^- 



36. 



The fish which is thus named is generally regarded as a hybrid between 

 Ckondrostoma nasus and Leuciscus muticellus. It is very variable, and 

 sometimes resembles one of these species and sometimes the other. 



