On a new Pa'cili'ul Fish from the Ainazoyr. 059 



Ty)->e. Adult female. Original number 2188. Collected 

 on June l^rd, li)ll. 



This Tkamnomys is undoubtedly related to the large 

 Ruwenzori species, T. venusttts, from which it is distin- 

 guished by its greater size and far larger mular teeth. 



LXXIII. — ^-1 nexo Pivciliid Fisli from the Amazon^ icith Notes 

 on the Genera Petalosoma and Tomeurus. By C. Tate 

 Kegan, M.A. 



(Published by permission of the Trustees of the British Museum.) 



In .1908 (Ann. & Mag. Nat. Hist. (8) ii. p. 458) I described 

 a Pceciliid fish from Costa Rica unclor the name Petahsoma 

 cultratian ; this dilTered from all other Poeciliids then known 

 in having the tail beliind the anal tin compressed to a sharp 

 ventral edge formed of paired scales. In the following year 

 Eigenmann (Ann. Carnegie AIus, vi. p. 53) published the 

 description of 2 omeurics gracilis from British Guiana, another 

 PoBciliid fish with this peculiarity. I l.ave now received 

 from Ilerr A. Kachow, of Hamburg, examples of a new 

 species of Petalosoma from the Amazon at Obidos. 



Pttalosoma and Tomeurus resemble Gambusia in mouth- 

 structure, dentition, &c., and in having the anal fin of the 

 male advanced and modified into an intromittent organ. In 

 Petalosoma the body is moderately deep (depth 3 to 4 in the 

 length) ; the anal fin of the male is inserted below or a little 

 behind the end of the pectoral, is rather short (| to 1 the 

 length of the fish), and has the elongate rays simple ; the 

 pelvic fins are well developed, inserted below the middle of 

 the pectoral, larger in the male than in the female. In 

 Tomeurus {fide Eigenmann) the body is long and slender 

 (depth 6^ in the length), the anal fin of the male is inserted 

 below the base of the pectoral, is very long (^ the length of 

 the fish), and has the first elongate ray armed with spiui- 

 ferous appendages, whilst the pelvic fins in the male are 

 minute, below the gill-openings, and in the female absent. 



The new species may be designated 



Petalosoma amazonum, sp. n. 



Body moderately compressed, its depth 3f in the length ; 

 length of head 4^. Snout as long as eye, the diameter of 

 Avhich is 3 in the length of head and less than the intororbital 



