566 ME. J. "VV. DAVIS ON A NEAV SPECIES OE COCCODrS. 



The head and anterior part of the body are protected by osseous 

 plates of considerable thickness and strength, surmounted at the 

 occiput by a large and massive spine. The spine is situated near 

 the middle of the back at a distance of 0*04 m. from the tip of the 

 snout. It rises to a height of O'Olo m. from the dorsal surface, 

 and is inclined at a very slight angle backwards. The anterior part 

 of the base of the spine is connected with the osseous plates of the 

 cranium by a broad expansion of its surface, which is overlapped by 

 the cranial bones. The surface of the spine is ornamented by 

 longitudinal striations, parallel with its anterior margin : the striae 

 on the posterior portion disappearing along that surface. The 

 posterior margin of the spine is armed with a series of nine or ten 

 denticles — long, pointed, and robust, equal in length to the diameter 

 of the spine in its upper part. The denticles are all inclined up- 

 wards, at an angle with the spine of about 45 degrees. 



The orbit (Or.) is medium -sized, situated very high, and at a 

 distance of 0-023 m. from the extremity of the snout. The inter- 

 orbital space is occupied by one or more osseous plates, extending 

 from the base of the spine to a distance in advance of the orbit. 

 Connected with this is a long plate terminating in a sharp-pointed 

 snout, and probably overlapping the maxillary bone (Mw.). The 

 surface of this bone, and also of those occupying the interorbital 

 area, is covered with minute tubercles, arranged more or less in lines 

 parallel with the longer axis of the plates. The under surface of 

 the head is covered with a series of plates : the most anterior is 

 probably the mandible (Mn.). It does not extend so far forward as 

 the maxillary bone, and its posterior portion assumes a Y-shaped 

 form : the upper branch, extending parallel with the maxillae, may 

 be the dentary, whilst the lower and longer branch probably 

 constitutes the articular bone. Between the orbit (Or.) and the oper- 

 culum (Ojy.) is a series of bones, which in this specimen are some- 

 what indeterminate. The space between these and the lower jaw 

 is not very well-preserved : • but there are indications of a large, more 

 or less triangular plate, whose under surface was covered by a series 

 of lines radiating from above dowuAvards, and covering the region 

 occupied by the mandibular suspensorium. The gill-cover is large, 

 and consists of preopercalum {Pop.), operculum {Op.), and probably 

 suboperculum {So]!.). The anterior margin of the preoperculum 

 {Fop.) is almost straight, and extends in an oblique line from the 

 anterior base of the spine to the posterior extremity of the mandible. 

 It is a long and narrow bone ; attached to its posterior margin is 

 the operculum {Oj).), larger in size, and with a circular posterior 

 margin extending forwards beneath the preoperculum. The 

 surface of both is covered with minute tubercles arranged in lines. 

 The space beneath the operculum may have been occupied by the 

 suboperculum. Behind the operculum and extending to the 

 abdominal aspect of the body is a large bony plate representing the 

 clavicular portion of the scapular arch {So.). The posterior extremity 

 of the bone forms a process extending considerably backwards ; its 

 upper portion is enveloped by the operculum ; its surface is orna- 



