288 CROCODILIDiE. 



Crocobiltjs planirosteis, Graves, Ann. Gen. Sc. Plojs. ii. p. 348 

 (1819). 

 Crocodilus o:i'aYesii, Bon/ de St. Vine. Did. Class. iVHist. Nat. v. 

 p. 109 (1824) ; Bum. '^- Bibr.ui.'^. 101 (1836). 



Hal)it remarkably stout. Snout short, perfectly flat above, with- 

 out ridges. Four anterior nuchals on a transverse series and six 

 posterior on two transverse series. Dorsal scutes in six longitudinal 

 and 18 transverse series, with vei'y strong, tubercular or recurved 

 keels ; lateral scales obtusely keeled. Scales on upper surface of 

 limbs keeled, tubercular. Toes entirely webbed. No cnemial crest. 



4. OSTEOL^IMUS. 



Osteolasmus, Cope, Proc. Ac. PJdlad. 18G0, p. 549 (1861). 

 Ilalcrosia, Gratf, Ann. 8) Mac/. N. H. (8) x. p. 273 (1862), and 



Cat. Sh. llep't. ii. p. 19 (1872). 

 Crocodilus, part., Sirauch, Si/n. Crocod. p. 28 (1866). 



10 or 17 upper and 14 or 15 lower teeth on each side; fifth 

 maxillary tooth longest; fourth mandibular tooth fitting into a 

 notch in the upper jaw. Snout rather short; nasal bones forming 

 a septum dividing the nasal aperture; supratcmporal fossae very 

 small ; a bony plate occupying the greater part of the upper eyelid. 

 Splenial bones not entering the mandibular symphysis, which ex- 

 tends to the fourth or fifth tooth. A dorsal shield formed of four or 

 six longitudinal scries of juxtaposed, keeled, bony scutes ; gular and 

 ventral scutes bony, not articulating together. 



West Africa. 



1. OsteolsBinus tetraspis. 



Osteolsemus tetraspis, Cope, I. c. p. 550, and Proc. Ac. Philad. 1867, 

 p. 209, and Tr. Am. Phil. Sac. (2) xiv. p. 85, fig. (1870). 



Crocodilus frontatus, A. Murray, Proc. Zool. Soc. 1802, p. 213, 

 pi. xxix. ; A. Ihim. N. Arch. Mas. i. Bull. p. 38 (1864) ; Straueh, 

 I. c. pp. 37 & 84, pi. — , and Bull. Ac. St. Pctersb. xiii. p. 51 (1869). 



Halcrosia froiitata, Graj/, Ann. ^- Mar/. X. II. (3) x. p. 273 (1862). 



nigra, Gra)/, Trans. Zool. Soc. vi. p. 153, pi. xxxi. figs. 1-6 



(1867), and Cat. Sh. Pcpt. ii. p. 20 (1872). 



afzelii, Lilljeborg, Proc. Zool. Soc. 1867, p. 715, figs. 



Head once and a half to once and two thirds as long as broad ; 

 snout obtuse, its length exceeding a little its basal width ; upper 

 surface deeply honeycombed, without ridges ; interorbital space 

 deeply concave, narrow. Nuchal shield distinct from the dorsal, 

 composed of two or three pairs of strongly keeled scutes, the ante- 

 rior of which are very large ; anterior part of nape with small, 

 scattered, keeled bony tubercles, the largest of which may form a 

 transverse series. 17 transverse series of dorsal scutes, the broadest 

 composed of six scutes : keels very feeble on the two median series, 



