FISHES — CESTRACIONTIDAE — CESTRACION FRANCISCI. 365 



CESTRACION, Cuv. 



Gen. Char. — Head thick, short, and rounded ; body fusiform, and tapering posteriorly. Nostrils split up to the edo-e of the 

 mouth, surrounded by a protuberant membrane, the outer one rolled inwardly, the inner one separated from the upper lip by « 

 groove; pupil, obliquely inclined backwards. The disposition of the teeth is pavement-like, the middle ones exhibiting frojn 

 three to five prongs, the lateral ones smaller than the central. Spiracles small, situated beneath and somewhat behind the orb:l. 

 Eye placed under a ridge extending from the snout to the tympanic region. The branchial apertures diminish in size backwards 

 he last two placed rather high up above the pectoral fins. Caudal fin short, with well developed lower lobe. 



Stn — Cestracion, Cuv. Rt-gn. Anim. H, 1817, 129 ; 2d ed. II, 1829 ; &, ed. illustr. Poiss. 365.— Agass. Rech. Poiss.foss 

 III, 1833, 168.— Miii.L. & Henle, Syst. Beschr. Plagiost. 1841, 76.— Dum. Ichthyol. analyt. 1856, 122. 



Up to a rather recent period the " Port Jackson shark" stood as a solitary species in Ihiw 

 genus. The " Voyage de la Venus" (Zool. 1855, 350, pi. x, fig. 2,) has made us actiuainted with n 

 second species. A third, whose description follows, was obtained on the coast of California, 



CESTRACION FRANCISCI, Grd. 



Spec. Char. — He.ad contained six times and a half in the tot.al length ; supni-ocular ridges very compact and prominent. 

 A cartilaginous fold or thickening at the anterior angle of the mouth as well as posteriorly. Anterior margin of first dorsal 

 nearer the extremity of the snout than the anterior margin of the second dorsal. Origin of anal equidistant between the tips 

 of the caudal and the insertion of the pectorals. Yellowish grey above ; light yellowish beneath, with small rounded and 

 scattered spots. 



Syn. — Cestracion francisd, Grd. in Proc. Acad. Nat. Sc. Philad. VII, 1851-, 196. 



We have before us two specimens of this species, the largest of which measuring nearly twenty- 

 seven inches. It bears a very strong resemblance to C. pliilippi, or "Port Jackson shark," 

 from which it chiefly differs by more prominent and compact supra-ocular ridges, a more back- 

 wards position of the ventrals and anal fin with reference to the dorsals, and larger pectoral fins. 

 So much as to the external appearance. The teeth exhibit generally three, sometimes five, 

 prongs^ the middle being always proportionally more developed than in the species to which we 

 are comparing it. 



The head is contained six times and a half in the total length. The snout is broad, very 

 declivous, and obtusely rounded oif. The supra-ocular ridge is not a mere fold of the skin, but 

 assumes a very hard structure, and considerably more raised above the orbit than hence forwards. 

 The inter-ocular space is depressed, sub-concave, from the occiput, where broadest, to the margin 

 of the snout towards which it tapers. The orbit is elliptical; its longitudinal diameter entering 

 about six times in the length of the side of the head ; the pupil, as already stated, being sub- 

 vertical, obliquely inclined backwards. The spiracles are small, situated somewhat below the 

 eyes, and posteriorly to a vertical line drawn immediately behind the orbit. The width of the 

 mouth is nearly equal to the inter-orbital space. The structure of the nostrils resembles very 

 much that of tlie same parts in G. pliilippi. The angles of the moutli are formed, anteriorly or 

 superiorly, by a thickened fold of the upper lip, extending somewhat beyond a thickening of the 

 posterior or lower lip, which constitute their opposite border. A short and shallow groove may 

 be seen directed obliquely outwards from the angles of the mouth. The second branchial 

 aperture is placed slightly in advance of the anterior margin of the base of the pectoral fin; the 

 three remaining ones being situated posteriorly to the same margin. The five of these apertures 

 are placed gradually one above the other from forwards backwards, diminishing in size in the 

 same directions. 



The body, as well as the head, appears proportionally stouter than in C. pJdlippi. All the 



