ILLtENUS. 



209 



Young specimens present nearly the same proportions, but the tail is somewhat shorter 

 and the form less convex. 



Localities. — Wenlock Limestone of Dudley, and the Malvern Hills, frequent. It is 

 probably common enough in the Wenlock of other places ; but I avoid quoting localities 

 which may belong to //. Barriensis. 



Foreign. — Niagara Limestone of Illinois and Wisconsin. 



[Illanus orbicaudatus, BiUings {' Catal. Sil. Foss. Anticosti,' 1866, p. 27), is a 

 Bumastus so like this that I do not see readily how to distinguish it. It is a Caradoc 

 and Llandovery form, in the Island of Anticosti ; but several of our fossils immigrated 

 from the far west in Silurian times ; and this may be one of the colonists.] 



Ill^nus (Bumastus) carinatus, n. sp. PI. XXVII, figs. 8, 9. 



[Compare with the kindred species, II. armatus, Hall}'\ 



Fig. 54. 



//. {B.) modicus 2 — S-uncialis ; capite rotundato gihbo carinato, angulis brevispinosis. 

 Caput gibbosim antice rotundatum, margine acuto nec recurvo, vertice gibbo carinato ; sidcis 

 axalibus primmn convergentibus, dein lente divaricatis et in foveas desinentibus. Oculi 

 parvi, pulvillo tumido instructi. Anguli in spinas crassas tracti, qua breves sunt et 

 striates. [Cauda forsan transversa^ 



This remarkable species, of which we only have two fragments in the Museum of 

 Pract. Geology, and another in Mr. Edgell's fine collection, is one of the rarest of the 

 Wenlock Trilobites. It was detected by myself, after lying for years in the Museum of 

 Pract. Geol. as a variety only of //. Barriensis : a good instance of the desirability, in a 

 public collection, of preserving all the variations that occur, and not reducing the 

 number too greatly. The late Rev. Mr. Dyson, of Malvern, 

 found our specimens in the Winning's Quarry, Malvern. It is 

 closely allied to an American form lately described by Prof. 

 Hall, referred to above ; and it may possibly be identical, but 

 differs in the facial suture, and in the proportions. Por points 

 of difference from British species, see pp. 204 — 207. 



Comparing our specimens, such as they are, with Prof. 

 Hall's smaller species, I find the following differences, that 

 make me hesitate to unite them. Ours is more gibbous on the 

 vertex, has much smaller eyes, set on a more protuberant 

 cushion ; and the facial suture in front of them cuts the 

 margin in advance of the eye — not at right angles to it. Prof. 

 Hall's description is, as usual, far too short and general ; he gives no note of the 



Illmnus (Bum.) armatus. Hall. 

 Niagara group, Wisconsin. 



1 18tli Report New York State Cabinet, printed in advance, Dec, 1864 (see description oill. Barriensis). 

 27 



