238 silxtrid^. 



length is contained thrice and a third in the total (without caudal) ; 

 the diameter of the eye is two-fifths of the width of the interorbital 

 spacej, Margin of the snout soft and naked anteriorly ; laterally 

 with small spiny scutes, the bristles becoming a little longer on the 

 interoperculum , margin of the operculum not serrated. The lower 

 side of the head, thorax, and belly entirely naked. Dorsal fin longer 

 than high, the length of its anterior rays being two-thirds of that of 

 the head ; the length of its base is more than its distance from the 

 second fin ; there are seven scutes between the two dorsal fins. 

 Caudal obliquely truncated. The pectoral spine does not extend to 

 the root of the ventral. Ten scutes between anal and caudal ; scutes 

 of the body finely granulated and striated, without keels ; post- 

 humeral ridge very obtuse. Uniform dark brown. (According to 

 Valenciennes, a series of white spots in each interval between the 

 dorsal rays.) 

 Guiana. 



a. Five and a half inches long. British Guiana. Presented by Su- 

 fi. Schomburgk. 



/3. Teeth few in number, much dilated at the crown. 



15. Plecostomus cochliodon. 



Cochliodon hypostomii9, Heckel, MS. 



Hypostomus cochliodon, Kner, Hypostom. p. 265. taf. 2. fig;. 1. 



D. 1/7. A. 5. .P. 1/6. 



The length of the head is not quite one-third of the total (without 

 caudal) ; occiput and nuchal region elevated. The free margin of 

 the opercles with small spines ; scutes of the body keeled, the keels 

 being serrated. Jaws with only seven or eight short teeth on each 

 side, which terminate in a dilated spoon-like crown. Throat, thorax, 

 and belly covered with small scutes. Dorsal fin as high as long ; 

 there are five or six scutes between the second dorsal and the caudal. 

 The pectorals extend beyond the base of the ventrals, and their outer 

 ray is armed with long curved spines ; caudal with the lobes of 

 nearly equal length. Yellowish brown, with a few scattered round 

 brown spots. {Kner.) 



Rio Cujaba. 



94. LIPOSARCUS. 



This genus agrees in all the characters with Plecostomus, having 

 the interoperculum entirely destitute of spines, but there are thirteen 

 or fourteen rays in the dorsal fin. 



Surinam and Brazil. 



1. Liposarcus multiradiatus. 

 Hypostomus multiradiatus, Hancock, Zool. Journ. iv. p. 246. 

 D. 1/13. A. 5. P. 1/6. V. 1/5. L. lat. 29. 

 Head not depressed, its length being two-sevenths of the total 

 (without caudal) ; a rather prominent ridge runs from the eye to 



