272 PROCEEDINGS OF THE ACADEMY OF 



This genus is Doras with tlie expanded dermo-ossified sternal 

 shield of the following genus Physopyxis. It forms a group con- 

 necting the two, and differing from the latter in not having the 

 lateral scuta meeting on the dorsal line. In one specimen there 

 is no adipose fin, in a larger there is a rudiment. As in Doras, the 

 postclavicular process is more extensively developed than the 

 postcoracoid, while in Physopyxis the latter is developed at the 

 expense of the former. The Zathorax monitor constitutes speci- 

 fically a linlv between such Dorades as D. grypus and the Physo- 

 pyxis lyra, in being of stouter form than the former, but less squat 

 and toad-like than the latter. It has the comb-like preorbitals of 

 the latter. 



Only one species is known. 



ZATHORAX MONITOR, Cope, sp. nov. 



Twenty-five short lateral scuta, each with one strong recurved 

 median spine. Casque broad, furcate to receive the dorsal fin, 

 obtusely roof-shaped to between the orbits, where it is a little 

 concave, weakly rugulose and striate. Preorbital bones with 12 

 processes above, not dentate on the lower margin. Muzzle broad, 

 short, lips even, mouth reaching to opposite front of preorbital. 

 Beards on the chin normal. Maxillary barbel reaching to poste- 

 rior margin of orbit, but possibly further in a harder specimen. 

 Orbit 3.15 times in head, 1.66 in interorbital width; head 3.75 

 times in length without caudal, twice to third lateral scutum. 

 Greatest depth (at dorsal spine) 3.5 in length. Postclavicular 

 spine extending to line of posterior process of casque, furnished 

 with a row of distant strong teeth on the outer edge. Humeral 

 swelling enlarged laterally, giving unusual width to this region. 

 Postclavicular spine short, acute, sternal shield transversely 

 striate, twice as wide as the gular region in front of it. 



Radii D. I. 6, the spine trigonal, straight, not serrate before or 

 behind, but striate; C. ?14; A. 12. P. I. 6, the spines large, 

 reaching beyond end of ventrals, with numerous close-set teeth 

 or spines on both edges, and a terminal one; surface striate. 



Total length .038 m., width at shoulders .013 m., at canthus oris 

 .0053. Length dorsal spine .008, of head and casque .016. The 

 larger specimen is .052 in length. 



Color destroyed by the action of the spirits; pale brown, the 

 pectoral spines dark-spotted. 



[January'' 16, 



