GILBERT AND ST ARKS — FISHES OF PANAMA BAY 17 



of ventials. The amount of exsertion of the snout is very variable, the protruding 

 portion being sometimes short and broad, sometimes long and narrow. The 

 distance from eye to tip of snout is 05 or 3j in disk, measured as above. The 

 posterior insertion of caudal spine is very sligiitly in advance of middle of 

 tail (measured from anus). The bucklers on tail vary in the present speci- 

 mens from one to seven (eight in one of the types); they have not appeared 

 at birth, and are still undeveloped in a young specimen 15 cm. long. It will 

 probably be found that there is always a regular series of seven or eight of these 

 when they first appear, a variable number of them falling ofl later. In the adults, 

 those remaining are usually unequally spaced, the interspaces often showing the 

 scars of the lost bucklers. Minute asperities seem to be constantly present (at least 

 in females), and are most numerous in a strip extending along the median line of 

 disk. The teeth are much as in U. mundns, but are much more deeply grooved. 



In females the teeth are flat without cusp, each tooth witli a deep transverse 

 groove, the hinder margin of which is elevated to form a ridge crossing the tooth 

 transversely behind its middle. In the male, each tooth has a long acute median 

 cusp; those in the upper jaw deeply grooved from base to tip along their anterior 

 face, those in lower jaw transversely convex. In U. mundus the cusps of upper 

 teeth in the males are provided with shallow grooves on basal portions only, and the 

 transverse grooves on the flat teeth of the females are shallow, and followed by a 

 lower transverse ridge. In embryos of V. a^pidurus, the inner margin of spiracular 

 rim is much elevated and produced anteriorly into a long slender coiled lobe, pos- 

 teriorly into a much shorter projection. All trace of this raised rim disappears in 



the adult. 



24. Dasyatis longa {Gurman). 



Not rare. One female specimen preserved. 



Anterior margins of pectorals gently concave along the middle, becoming 

 convex toward tip of snout, the latter abruptly projecting. The cutaneous fold on 

 lower side of tail is low, not over 3 mm. in height; it begins opposite the anterior 

 insertion of caudal spine, and is evident on about half the length of the tail. An 

 extremely low ridge on back of tail behind caudal spine. The tail is very rough 

 behind the caudal spine. A series of 34 coarse, spinous tubercles on median line 

 of back, the three largest at intersection of median line with shoulder-girdle. 

 Opposite this point are two short series of much smaller tubercles converging slightly 

 backward. In addition to these, the interorbital region and the median area of back 

 contain numerous stellate prickles, but few of which are behind the shoulder-girdle. 



mm. 



Length of disk 355 



Width of disk 420 



Tail (from anal sHt) evidently broken 790 



Tip of snout to middle of nasal flap 80 



Outer edge of ventrals 60 



Anterior margin of pectorals 260 



Longitudinal diameter of eyeball 20 



Length of spiracle 25 



Width of cartilage between eyes 38 



