FISH. 1 1 1 



itself is twice the length of that fin ; very low at first, but gradually rising, until, before its 

 termination, it becomes equal to between one-half and one-third of the depth. The vent is in 

 the middle of the entire length, caudal excluded. Anal short, and just beneath the middle of 

 the adipose, there being about one-fourth of this last fin in advance of it as well as behind it : 

 the first four rays simple, but apparently all articulated, the first two or three very minute and 

 not easily observed. Caudal forked for two-thirds of its length : the upper lobe a little longer 

 than the lower, and contained five and a half times in the entire length. Ventrals imme- 

 diately beneath the last ray of the dorsal ; a little shorter than the pectorals, and not reaching 

 to the anal by half their own length. 



D. 1/6 ; A. 14 or 15 ; C. 17, &c. ; P. 1/9 ; V. 6. 



Length 5 inches 2 lines. 



Colour — {Inspirits.) Brownish, inclining to silvery in some places: a dusky fascia formed of 

 dots along the lateral line. Dorsal rather dusky at the base, and with the upper portion also 

 dusky between the rays : a dusky spot on the anterior part of the adipose. 



Habitat, Rio de Janeiro. 



This species was taken by Mr. Darwin in a running brook at Rio de Janiero. 

 It approaches on the whole so nearly the P. gracilis of D'Orbigny, that I can 

 hardly suppose it to be distinct. Yet there are some slight differences observ- 

 able in this specimen. It has more anal rays ; the adipose appears shorter ; and 

 the upper lobe of the caudal is not so prolonged, though possibly it may be worn 

 down. Also D'Orbigny's figure appears to want the dusky stains on the dorsal 

 and adipose fins. If it be not that species it must be new, as there is none other 

 described by Cuvier and Valenciennes with which it will assimilate better. 



2. PlMELODUS EXSUDANS. Jen. 



P. corpore parum elongato, altitudine quintam partem longitudinis cequante: galea 

 loevi, inconspicud, processu interparietali haud clypeum parvum pradorsalem attin- 

 gente : poris paucis buccalibus amplis, serie obliqud dispositis : maxillis cequalibus : 

 cirris sex ; maxillaribus haud analem attingentibus : lined laterali primum deflexd, 

 deinde recta : pinnis dorsali et anali brevibus ; adiposd dorsali haud duplo longiore : 

 caudal i profundi bijurcd, lobis cequalibus : spina pectorali margiue interno for titer 

 dentato. 



D. 1/7 ; A. 13 vel 14; C. 17, &c. ; P. 1/8 ; V. 6. 

 Long. unc. 3. lin. 6. 

 Foum. — In some respects resembling the last species, but the body much less elongated, the depth 

 and thickness remaining the same. The depth is about one-fifth of the entire length ; the 

 head rather more than one-fifth. The helmet is scarcely so much wrinkled, and the inter- 

 parietal process not so long, reaching only half-way to the buckler, which last is smaller and 

 less obvious. The solution of continuity of the bones of the cranium appears to extend back 



