32G On the Osteology the. of tlii Onl'V Microcyprini. 



moved to one side than the otlier, Is usually somewhat curved 

 towards that side, and is otherwise not quite symmetrical; 

 the urogenital orifice of the female appears to be median and 

 symmetrical. 



6. Anablbpin^. 



The remarkable genus Anableps, with three species from 

 Central and South America, shows relationship to Jenynsia 

 in tiie structure of tiie intromittenfc organ, but has a number 

 of other characters which are unique in the suborder. The 

 eyes are divided transversely into an upper and a lower 

 portion, the former raised above the surface of the head and 

 adapted for vision in the air. The skull is flat, so depressed 

 that in the orbital region the broad parasphenoid and the 

 frontals are separated by a scarcely perceptible interspace ; 

 the frontals are raised above the orbits ; there are no post- 

 cleithraand the pelvic bones are well separated; the vertebrgo 

 are numerous (46 to 53), the prteoaudals with strong para- 

 pophyses which are grooved superiorly and have the ribs 

 attached near their distal extremities. 



Garman's account of this genus ('The Cyprinodonts,' 

 pp. 70-79, pis. vi. & vii.) is of considerable interest; he has 

 shown that both males and females are " rights and lefts ; "_^ 

 in Anableps anableps the female urogenital orifice is covered 

 by an enlarged scale, unattached on one side or the other, so 

 as to open to the right or left ; presumably dextral malei 

 pair with sinistral females, and vice versa. 



7. PcECILIINM. 



The fishes of this subfamily differ from all the others of the 

 order in the absence of exoccipital condyles. They are vivi- 

 parous, and in the malt s the anal fin is advanced and modified, 

 some of the anterior rays being enlarged and produced. 

 Eigenmann has studied the structure of this intromittent 

 organ in the Pceciliids of the La Plata (Proc. U.S. Nat. Mus. 

 xxxii. 1907, p. 425) ; he has found that it is the third, 

 fourth, and fifth rays which are prolonged ; these rays may 

 be rolled up to form a tube, or they may be armed with 

 recurved hooks or with terminal finger-like or antler-like 

 processes. The anal fin of the male is supported by special 

 bony stays, 2 to 5 in number, which project downwards and 

 forwards from the bridges connecting the parapophyses of 

 some of the posterior prsecaudal vertebrae (cf. Grarman, * The 

 Cyprinodonts,' pi. viii.). 



The osteology is much as in the Funduliiu'e, except for 



