172 CALIFORNIA ACADEMY OF SCIENCES. 



Remabk. — Since writing the above, we have studied the 

 SiluridcB Opisthopterce of Giinther (^= Trichomicteridce). The 

 genus Heptapterus cannot be retained in the 1 richomideridce. 

 It is very closely related to Rhamdella, which should be 

 raised to generic rank. In Heptapterus the modified ante- 

 rior vertebrae have simple lateral processes beneath which 

 the air-bladder lies free in the abdominal cavity, as in the 

 Siluridce proper. In Trichomicteridce the anterior vertebrae 

 are coalesced, but the lateral processes are greatly compli- 

 cated, forming a closed capsule in which is concealed the 

 pair of small round air-bladders. Leaving out of consider- 

 ation the position of the dorsal in its relation to the ventral 

 fins, Hepapterus and also the genus Nannoglanis Boulenger 

 possess all the characters which define the group Pimelodine 

 Giinther. That the relative position of the dorsal and ven- 

 tral fins is of no great importance may be gathered from a 

 comparison of the following plates: Liitken, Rio das Velhas 

 Flodens Fiske, pi. Ill, figs. 6-7; Steindachner, Flussf. 

 Siidam. Ill, pi. V, fig. 1, and Boulonger, Proc. Zool. Soc, 

 1887, pi. XXI, fig. 3, representing the genera Pimelodella, 

 Heptapterus and Nannoglanis. After Rhamdella should 

 therefore be inserted ^^ 



^. 



Via. Heptapteeus Bleeker. 



36a. Heptapterus mustelinus Valenciennes. 



• '^ , Locality: Maldonaclo. 



36b. Jleptapterus surinamensis Bieekar. 



36c. Heptapterus COllettii steindachner. 



VI&. 'Nannoglanis Boulenger. 

 36d. Nannoglanis fasciatus Boulenger. 



