542 BRITISH FOSSIL REPTILES. 



obtusely tenninated snout, as if it had been cut short, giving the character of the Ptero- 

 saurian family Truncirostres} The species of this family which have the foremost pair of 

 teeth projecting forward in the upper jaw from the truncate surface at a higher level than 

 the alveolar border form the genus Cohhorhynchus? 



B. — CololorJiyncJms cJavirostris, Owen [Pterosauria, Plate 19, figs. 1 — 4). 



In two species of these large Pterodactyles from the Cretaceous series, viz. Colobo- 

 rliynchm Cuvieri, from the Middle Chalk of Kent,^ and Colohorhynclms Sedgwickii,^ from 

 the Upper Greensand of Cambridge, the anterior pair of teeth of the upper jaw project, as 

 in the present species, from the fore part or end of the premaxillary, and are dii-ected 

 forward with a slight downward curve. 



In a still larger species {Criorhi/nchiis simug"), from the Upper Greensand of 

 Cambridge, the foremost pair of teeth project from the under surface of the fore end of the 

 premaxillary, and are directed downward like the following teeth. The fore end of the 

 premaxillary was fortunately entire, showing a flattened or feebly concave tract corre- 

 sponding to the part bored by the anterior alveoli in Colohorhynchus. Some reserve may 

 be prudently entertained as to whether a pair of teeth so anomalously located as iu 

 Colohorhynchus might not be shed without replacement by successors ; and the geiuis 

 Criorhynchiis is to be accepted with this reserve, which future discoveries may dissipate. 

 The manifestation by a ' truncirostral ' Pterodactyle of the Wealden, and by another 

 from the 'Greensand,' of the produced and unopposed pair of teeth from the front surface 

 of the muzzle, have dissipated the doubts as to its accidental and individual character which 

 legitimately attached to the first specimen, from the Chalk, in which it was observed. 



Colohorhynchus clavirosfris is, at present, represented by the fore part of the upper 

 jaw of a Pterodactyle {Pter., PI. 19, figs. 1 — 4) from the Wealden, of equal size with Crio- 

 rhynchus simus, from the Upper Greensand, but in which the small anterior pair of 

 premaxillary teeth project from the front surface of the bone, and at a greater elevation 

 above the palate and the sockets of the second pair, than in Colohorhynchus Cuvieri or 

 Coloh. Sedywickii. 



The flattened fore part of the premaxillary (ib., flg. 2) is broader and of less height in 

 Colohorhynchus clavirosfris before the narrow upper surface [g) begins to slope backward 

 to the upper contour of the cranium. The anterior median depression (h) is shorter 



1 Mihi (Truncus, cut short). 



2 KnXopus, stunted ; pvyx^os, snout. 

 ^ Pterosauria, PI. 3, figs. 1 — 7. 



•• lb., PI. 7, figs. 1, a—(i. 



* Pterosauria, PI. 11, figs. 1—5. 



