146 W. Davies — On Squaloraia. 



regard to them in the respective descriptions of the before-named 

 authors. 



Dr. Eiley observes, that " in front of the ' fontanelle ' are two 

 terminal prolongations. The superior has been fractured at its 

 posterior extremity, and thrust backwards as far as the anterior edge 

 of the orbits. It is elongated, conical, flattened posteriorly and 

 superiorly, but becomes more rounded towards its anterior extremity. 

 Firmly attached to its superior surface are many of the small 

 spines already noticed. In its displacement it has been moved 

 obliquely backwards, so that we are able to observe the superior sur- 

 face of the inferior prolongation. 



" This prolongation is likewise elongated and conical ; its length 

 was probably greater than the preceding, for its anterior extremity 

 is broken, and has been lost. The superior surface, instead of being 

 convex like the former, has a very wide and superficial groove, the 

 boundaries of which are the, edges on each side, elevated into a cor- 

 responding ridge. 



" These ridges are higher and wider posteriorly than anteriorly. 



" The form of these terminal cartilages in the Bhinobatus is, in 

 their essentials, like that of our specimen." ^ 



Agassiz says, " That the great prolongation of the anterior part 

 of the head is not formed by the jaws, as Dr. Eiley thinks ; it is a 

 beak (hec) similar to that of the Scies (Pristis), or rather analogous 

 to the beak of the genus PristiopJior^is of MM. Mtiller and Henle. 

 It is composed of two parts, the lower and lai'ger one depressed 

 along the centre in such a way as to be able to receive the other, 

 which is rounded. Around the beak one sees small spines similar 

 to the ' boucles ' of the Eays." ^ 



From the foregoing extracts it is evident that both Prof. Agassiz 

 and Dr. Eiley considered that these two "prolongations" formed 

 one beak or snout, the upper united at the " depression along the 

 centre" to the lower. Examples in the National Collection show 

 that they were not thus united, but that they really formed two 

 unconnected processes. 



Upon a close examination and study of the head of the new 

 acquisition, I was impressed with the spine-like appearance and 

 structure of the upper "prolongation," and, also, although it now 

 rests — but somewhat obliquely — upon the inferior, that it was origin- 

 ally free or detached from it for the larger portion, if not along its 

 entire length ; and that this inferior "prolongation " has all that portion 

 which is exposed of tlie upper surface covered with the dermal in- 

 tegument, which integument is also continuous beneath the upper 

 " prolongation." This superior process is bare, with the exception of 

 the radiated tubercles upon its upper surface, which show that it was 

 a true external surface, and not covered by the skin. Eeferring 

 to Agassiz's engraving of the specimen in the Bristol Institution, 

 and which appears to have been carefully and accui'ately drawn, 

 (the head of which has been reproduced by Mr. Griesbach upon 

 the accompanying Plate IV., Fig. 6, from Agassiz's Poissons 



1 Geol. Trans., 2nd ser., vol. v., p. 84. 



2 Eech. Poiss. Fobs., torn, iii., p. 379. 



