200 



SILURIAN TRILOBITES. 



tudinis ejus vix sejtmcti ; d marline postico distantiores. Anguli — ? Thorax cajoite 

 longior, e annuUs 10 latis confedus, quorum axis modicus, sulci axales profundi. Fulcra 

 proxima ; pleura recta, longitudinaliter striato-costata, apicihus truncatis. Cauda oUongo- 

 ovata, ad mediam partem gihha, angulis truncatis, axe brevi, angusto, superne conspicuo, intus 

 3 — ^-annulato. Margo caudce nequidem recurvus ; fascia lata concava, striis imbricatis 

 paucis imbricafa. 



It is sad patchwork reconstracting this species, though we have plenty of frag- 

 ments — heads without cheeks, a distorted but complete thorax, and several tail- 

 pieces, all of which show a strong granular character of the inner crust, which is 

 exhibited by short broken lines and puncta in the cast. Even fragments show this 

 character. The species is pretty common in the Coniston limestone ; and all who 

 know that rock know what a vast amount of cleavage and distortion the fossils have 

 undergone. 



Nor are we quite certain about the name. Eichwald's figure truly represents a 

 Scandinavian form distinct from the common //. crassicauda, and very much like ours, 

 with broad thorax-rings, and the eye placed near the fuiTows, and rather forward, com- 

 pared with such species as //. Bowmani, which occurs with it, and has no granular 

 surface. 



But in the 'Memoirs Geol. Survey,' vol. ii, pt. 1, when describing this species which 

 I had already distinguished and figured for Prof. Sedgwick's book (the figures quoted 

 are drawn by me), I unfortunately included with it and figured for it the //. MiircUsoni 

 described at p. 201. I gave it the same name in the Appendix to the ' Woodwardian 

 Synopsis ' above quoted, and thereby vitiated both descriptions. I must, therefore, go 

 over the ground again, as we usually have to do when in a hurry ; the Coniston limestone 

 species is the one intended, and should it prove distinct, as I think it will, from Eichwald's 

 fossil (which seems not to have occurred to Prof. Angelin in his Swedish collections), I 

 propose to name this conspicuous Westmoreland fossil //. Marshalli, after the gentleman 

 who has done so much to help forward tlie study of the Westmoreland fossils. 



It is larger than //. Boimiani, and nearer five than four inches long; of a lengthened 

 shape, both the head and tail semioval, with blunt extremities ; gibbous, especially in 

 front ; deeply trilobate, and marked all over the cast with short wavy impressed lines 

 and puncta. Tiie glabella-furrows are more direct, longer, and converge more than in 

 11. Bovmani (we need not compare it with //. Murchisoni, with which I formerly con- 

 founded it). The shape of the head is not very clear, but it is nearly as long as wide, very 

 gibbous forwards, and overhanging like that of //. crassicauda, which species it resembles. 



The glabella-furrows are sigmoid, but only slightly converging, and bent out above ; 

 they extend forwards twice as far from the posterior margin as the place of the eyes, 

 more than one third, but not half-way up the head (our filgure has them rather too much 

 curved). The small eyes arc [)laced about as far out from the glabella as half its width 

 (in //. Boxomani they are two-thirds its width away), and they arc placed once and a 



