428 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



namerous. The teeth in the upper jaw very irregular in size, and hardly 

 specialized, excepting in two patches at each side of the sympyhsis. 

 Two moderate sized canines in advance of these patches. Vomerine 

 teeth numerous and feeble. Palatine teeth very weak and with incon- 

 spicuous bands upon the crest of the bone. Preoperculum with mi- 

 nute denticulations, somewhat stronger at the angle. The length of 

 the intermaxillary is considerably more than half that of the lower jaw. 



Distance of insertion of dorsal from snout equals the greatest length 

 of head including the opercular flap, the dorsal origin being very slightly 

 in advance of the insertion of the ventral, which is located under the 

 base of the third dorsal spine. Length of third dorsal spine is equal to 

 that of the intermaxillary. 



Distance of anal from snout about equal to twice the length of the 

 head, the length of its base being slightly greater than the greatest 

 length of the pectoral. The second anal spine is the stoutest, and 

 is twice as long as the first, while the third, which is slender, is 2i 

 times as long as the first. 



Distance of pectoral from snout is one-third the standard body length. 



Distance of ventral from snout is equal to twice the postorbital 

 length of the head. The length of the ventral is slightly more than 

 one-eighth of the standard body length (one-sixth or more in smaller 

 specimens). 



The length of the middle caudal rays is equal to the distance from the 

 posterior margin of the orbit to the tip of the largest opercular spine. 

 The upper and lower lobes of the caudal produce an incurving, gi%ing 

 to the space between the lobes a semicircular outline. 



Scales in lateral line 130. Above lateral line 27-28; below, GO-61. 



Eadial formula.— D. XI, 16-17; A. Ill, 10-11; C. + 17 + ; P- I, 16; 

 V. I, 5. 



Full measurements of three specimens will be found in Proceedings 

 of the National Museum, Vol. II, p. 141. 



15. Hypoplectrus gemma, n. sp. 



A single specimen. No. 3422, of a new species of Plectropoma, has for 

 many years been preserved in the museum. Name of collector unknown. 

 In general appearance this species resembles Rypoplectrus nigricans of 

 Poey, a specimen of which from the same locality was found in the same 

 bottle and recorded under catalogue number 3423. In shape it is also 

 similar to Hypoplectrus pnclla, but its coloration appears to have been 

 much more uniform. The crescent-shaped caudal is a diagnostic mark, 

 by which it can be distinguished from all other species now accessible 

 to us. 



Description. — Greatest height of the body is contained 3 times in 

 its total length, and 2^ times in its standard length. Greatest width 

 equals length of second dorsal sphie; least height of the tail is con- 

 tained 3 times in the length of the head. The scales are small, weakly 



