NATURAL SCIENCES OF PHILADELPHIA. 443 



Subfamily POMATOMIN^E Gill. 



Genus POMATOMUS, Lacepede. 

 Gonenion Raf. 

 Temnodon Cuv. et Val. 



POMATOMUS SALTATRIX Gill. 



Gasterosteus saltatrix Linn. 



Scomber saltator Bloch. 



Cheilodipterus heptacanthus Lac. 



Pomatomus skib Lac. 



Gonenion serra Raf. 



Scomber plumbeus Mitchill. 



Temnodon heptacanthus Quoy and Gainard. 



Temnodon saltator Cuv. et Val. 



This species is very abundant along the entire eastern coast of the United 

 States. 



Description of a new generic type of MORMYROIDS and Note on 

 the arrangement of the genus. 



BY THEODORE GILL. 



The Mormyroids now known appear to be distributable among two sub- 

 families and eight genera which may be briefly distinguished by the following 

 characters : 



I. Dorsal very long, commencing in front of ventrals. Anal very short. 



Vomer covered by anterior processes of palatine bones. 



Cerebellum entirely concealed above Mormyrinje. 



Muzzle tubuliform Mormyrus. 



Muzzle obtuse Mormyrodes. 



II. Dorsal commencing more or less behind the ventrals. 



Anal oblong or elongated. Vomer uncovered. Ce- 

 rebellum and quadrigeminal bodies more or less ex- 

 posed Petrocephalin^e. 



A. Mouth considerably in advance of the eyes. 



1. Anal rather shorter than dorsal Isichthys. 



2. Anal less than twice as long as dorsal (D. 17-26. 



A. 25-50). 

 a. Lower jaw without flap or barbel. Upper jaw 



longer Marcusenius. 



Lower jaw prominent Mormyrops. 



p. Lower jaw with a conical flap or barbel Gnathonemus. 



3. Anal three times as long as dorsal. Palatal teeth 



pisiform Hyperopisus. 



AA. Snout produced. Mouth under eyes Petrocephalus. 



MORMYRINiE Gill. 



Mormyrus Linn. 

 Scrophicephalus Sw. 



Mormyrus caschive Hass. 



Mormyrodes Gill. 



Mormyrodes hasselquistii = Mormyrus hasselquistii Geoffroy, 



PETROCEPHALINJE Gill. 



ISICHTHYS-Gill. 



Isichthys henryi Gill. 

 1862.] 



