2. CHELMO. 37 



Skeleton. — The skull of Chelmo is at once distinguished by the 

 peculiar prolongation of the jaw-bones, in which, however, the max- 

 illary does not participate ; the latter is very much like that of a 

 species of Chcetodon, short, with the lower extremity slightly dilated, 

 anteriorly concave, posteriorly irregularly convex. A long and 

 slender process, directed forwards, extends from the palatine bone 

 across the upper extremity of the maxillaiy, and is received in a 

 notch of the prasorbital. The anterior portion of the intermaxiUaries, 

 as well as their posterior processes, are exceedingly elongated in a 

 horizontal direction, and both bones together fonn a half-channel, 

 similar to the bill of a bird, anteriorly with seven transverse bands 

 of minute teeth ; the anterior margin of the jaw, besides, is armed 

 with a series of very small teeth. The aiiicular and dentary bones 

 of the mandibula are hkewise exceedingly elongate ; the latter is 

 toothed Kke the intermaxillaiy, the articular anchjlosed to the hypo- 

 tympanic, prffioperculum and interoperculum. 



The other portions of the skeleton bear a great resemblance to 

 Chcetodon. The upper portion of the skull appears as a solid, ele- 

 vated, roimded bony mass, with a groove above each orbit. Sutures 

 are visible between the supraoccipital, principal frontal bone, and 

 suprascapula. The supraoccipital is continued posteriorly in a very 

 elevated and strong crest, which has the upper margin swollen, and 

 is posteriorly bifurcate, to receive the hook-like process of the first 

 interneural. The anterior fi'ontal bones are not to be distinguished 

 from the principal frontals ; the orbital margin is crenulated. 



The turbinal bones are well developed and elongate; the proe- 

 orbital is oblong, twice as long as high ; the remainder of the infra- 

 orbital ring is veiy naiTow, and its posterior poiiion firmly united 

 with the interior ridge of the praioperculum. The praeoperculum 

 has the interior ridge very slightly elevated, and the muciferous 

 channel merely indicated ; the limbs fonn an obtuse angle together, 

 and the length of the inferior is 1| in that of the posterior ; the 

 margins are obtusely seiTated. The operculum has neither ridge nor 

 spine, is sub quadrangular, and not quite twice as high as wide. The 

 sub- and interoperculum are veiy obliquely situated ; the former is 

 small, the latter broader anteriorly than posteriorly. The supra- 

 scapula is fii-mly joined to the bones of the skull ; the humerus is 

 well developed and sword-shaped. The coracoid has the outer ridge 

 considerably elevated, so that the cavity for the muscles of the pec- 

 toral appears rather deep ; there is only a small ovate foramen be- 

 tween the coracoid and ulna, the bottom of the cavity being entii-ely 

 bony. The lamellae of the pubic bones are nearly equally developed ; 

 the lower is swollen posteriorly for articulation with the ventral 

 spine. 



There are ten abdominal and fourteen caudal vertebrce, the length 

 of the former portion of the vertebral column being to that of the 

 caudal as 1 : l-o. The ribs are strong, anteriorly and posteriorly 

 with a groove, and at the base with a small epipleiu'al spine. The 

 longest neural and hsemal spines are those of the middle vertebrae, 

 and the latter are longer than the former. There are two very 



