14 Foord and Crick — On Prolecanites compressus. 



the septate portion of the shell, does not display the subangular 

 character of the peripheral edges, the two specimens which exhibit 

 this character best are only 138 mm. and 145 mm. in diameter respec- 

 tively. The same two examples show also the concavity of the 

 portion of the lateral area of the whorl adjoining the peripheral 

 region as well as the inflation of the sides of the body-chamber 

 observable in Mr. Wright's specimen. 



There cannot, therefore, be any doubt, we think, as to the species 

 to which Mr. Wright's specimen must be referred. It clearly 

 belongs to the species which Sowerby described as Ammonites 

 Hensloioi. 



(iii.) Comparison of Mr. Wright's specimen with Soioerhy's types of 

 Elltpsolites compressus. 



J. Sowerby figured two specimens to illustrate his species Ellip- 

 solites compressus ; as we have already stated, both figured specimens 

 are in the Sowerby Collection in the British Museum (Natural 

 History). In the larger of these specimens we have failed to find 

 any trace of the septa, but the general characters of the shell — its 

 evolute form ; the wide umbilicus ; the shape of the whorls, the 

 form of the periphery, the flattening of the sides, their feeble con- 

 vexity and the position of their greatest convexity, the nature of 

 the inner margin — agree so closely with those of Mr. Wright's 

 specimen that there cannot, we think, be any doubt of their 

 identity. 



In the small specimen figured by Sowerby the suture-line is some- 

 what indistinctly visible, as we have already remarked, at about the 

 commencement of the outer whorl. When this is compared with the 

 suture-line on the inner whorl of a large specimen of " Ammonites 

 Henslowi " at a point where the diameter of the shell is about the 

 same as that at the place where the suture-line is seen on the speci- 

 men, the two are found to closely resemble each other. The nature 

 of the surface of Sowerby's specimen, however, does not enable 

 us to follow its suture-line as well as we could wish, but the small 

 specimen agrees so well in its general form and rate of increase 

 with the larger specimen figured by Sowerby, and moreover is 

 from the same locality, that it is most probable they are examples 

 of the same species. 



The smaller of the two specimens has some resemblance to 

 M'Coy's figure of Goniatites discus.^ In the " [Sir Kichard] Griffith 

 Collection" of the Museum of Science and Art, Dublin, there is an 

 example of this species which agrees so well with M'Coy's figure 

 (except that the figure is reversed) as to size, form, and even the 

 fracture of the end of the last whorl, that it may be M'Coy's type, 

 although there is no information with the specimen to that effect. 

 It is a natui-al cast, partly buried in matrix. Although a portion of 

 the surface of the fossil has been ground away to show the suture- 

 line, this was still somewhat indistinct, but by slightly jDolishing the 



1 F. M'Coy, Synopsis of the Characters of the Carboniferous Limestone Fossils of 

 Ireland, 1844, p. 13, pi. ii. fig. 6. 



