ICHTHYOLOGY OP THE LESSER ANTILLES. 



475 



as in 0. trigonum and 0. ovinum. The inferolateral sides also expand or Bare out strongly at the middle of the 



length, making the abdominal width equal to the height. The horns are well developed. Superciliary ridges prominent, 



unarmed, interorbital region concave, front descending very 



steeply, slightly concave, not projecting beyond the promaxillary. 



Lateral scales a little higher than broad, all with a central clump 



and six radiating lines of sharply defined rounded tubercles. 



These cause a sharp serration of the dorsal ridge. Radii D. 10 ; 



C. 10 ; A. 10 ; caudal I'm truncate. Total length (axial) 0m. 11 ; 



of shell without muzzle and caudal peduncle O.m.O 75 ; greatest 



elevation of dorsal ridge (oblique) 0m. 055 ; greatest abdominal 



width Om.050 ; width at supercilia 0m. 018 ; total length caudal 



peduncle and Qn Om. 042. 



Color, light, brown, with a pale yellowish spot or area, near 

 the middle of each plate. A short chain-like band of dark 

 brown, enclosing yellowish graj areas, extends from below the 

 orbit to behind the axilla ; a similar but narrower parallel band, 

 exists at a point 8-5ths the distance from the last to the dorsal 

 fin ; in one specimen it is obsolete. Upper side of the caudal lin 

 closely yellow spotted. Fins unieolor. 



Three specimens from unknown locality. 



Fig. (I. Ostracium expansum, Cope. 



SI 



Fig. 10. Ostracium expansum, Cope. 

 This species has somewhat the form of 0. triquetrum, but is shorter and with superior and lateral ridges more 



convex or expanded. It differs from that species and O. lieaudale in having no distinct scales over the operculum, and 

 no fissure extending anterior to the latter, to permit movements of the respiratory apparatus.* 



are' convex above will t dorsal keel or tubercle. Depth between lateral angles JSgreatest width, tnterorbltal region plane 



ncave not orolectina distallv Orbit oval 2 :i-5 times in length of head, equal to length of muzzle that ta boxed, and equal to the 

 , „,lt. Scales with' rugose, radii, those beneath the orbit excavated. Length or head (to superior end i.l open mat slit) 4.1S6 times to end 



of caudal ill. Radii I) ')■ (! Ill A 'I Color above mid laterally brown below yellow. The sides closely marked with round blackish spolsin regular quincunx. 



oarts of three on each scale Belly with a larger brown spot In the centre of each scale. Front and sides and end of dorsal shield with small black spots; caudal 

 peduncle and fin mow,,, with black spots; other tins Immaculate. Total length 0m,118i of shell um.077; width above posteriorly Om.ull Interorbital width 

 om'OlBi greatest dorsal width Om.084, 



$X^™X*w& '£ S^'iLffi^SffSfiftr. according to Bleeker Intta more concave profile, and large ring-shaped .pots i, compared 

 with 0. punefciium, a has;, shorter muzzle and longer opercular silt (whence the name) the latter entering the former In tbaUpecles 2.6 times Instead ol once. 



*ClB0TIUM F 



Transverse 

 profile of muz 

 fength of the opercular sl1 



