NATURAL SCIENCES OF PHILADELPHIA. Sit 



BEOCHIS, Cope, gen. nov. 



Allied to the last genus. Two barbels at the extremity of the 

 maxillary bone, united by a beard-like looped cord to the sym- 

 physis mandibuli, the cord being thus attached at both end?. 

 Teeth rudimental or wanting. Body with two longitudinal series 

 of shields, the postcoracoids expanded and meeting on the median 

 line. Head compressed, the parietal shield only separated from 

 the dorsal spine by the basal azygos shield of the latter. Sides 

 of head shielded to the mandibles. Dorsal and pectoral fins with 

 strong spines ; adipose present, purgeut. Caudal fin emarginate. 



This genus is allied to Corydoras, but differs from it as Hoplo- 

 sternum does from Callichtlnjs with the addition of the peculiar 

 pendent dermal loops of the mandible. These loops are confluent 

 at the symphysis mandibuli, and from that point to their union 

 with the maxillary barbels resemble exactly the mental barbels of 

 Dianema. It is diflficult to avoid believing that these loops are 

 homologically the recurved inferior lips of Corydoras, separated 

 from the greater part of the ramus, but joining again at the can- 

 thus of the mouth and giving rise to the inferior barbel. It then 

 follows with much probabilit}^ that this connection also is severed 

 in Dianema^ and the inferior maxillary barbel remaining as before 

 continuous with the mandibular loop, becomes the mental barbel. 

 In the shielding of the head, Bi^ochis is like Corydoras^ while 

 Dianema is like Hoplosfernum, so that the affinities are compli- 

 cated and not readily expressed by a linear arrangement. 



BEOCHIS COERULEUS, Cope, sp. nov. 



Form short, stout, elevated, and compressed. Head steep, 

 gently convex above the orbits and concave above and below 

 them, and tapering to a very narrow muzzle, which overhangs the 

 mouth a little. Scuta, 23-21, smooth, with one oval supratempo- 

 ral shield only. Nares small, close to the orbits. One large com- 

 bined pre- and suborbital shield ; a large subtriangular loreal plate. " 

 Maxillary barbels extending to opposite the middle of the orbit. 

 Shields of the head, with the postcoracoids, slightly rugose. 



Length of head one-third length without caudal fin, 1.33 times 

 in greatest depth at basis of dorsal. Orbit four times in head, 

 more than twice in muzzle, which equals the wddth of the convex 

 interorbital space. The dorsal outline is strongly arched, de- 

 1872.] PART III.— 19 



