﻿98 



SILURIAN TRILOBITES. 



Fig. 21. 



is well marked (as in figs. 5 — 7). The cheeks gibbous anteriorly, but without any buttress 



opposite the middle lobe. The thorax convex, its axis as broad as 

 the sides; the fulcrum (as in C. TJlumenbacJiii) approximate. The 

 tail is trigonal ; but its sides slightly arched, — the axis convex, 

 not much tapering, abrupt at the end, and with six or seven 

 rings. The sides are deflected, but a little arched, and have five 

 ribs, forked thoughout. 



The whole surface is granulose (not roughly tubercular as 

 in C Blumenbachii), with larger and smaller tubercles. I think 

 C. callicephala, Green, Cast No. 2, is too extreme a form to be 

 reckoned with this subspecies, though closely allied. Hall says 

 it is identical, but the C. Blumenbachii of his work (C. senaria, 

 Conrad) is quite our species, and is as common in the Lower 

 Silurian Limestones of the Western States as in our own Caradoc 

 See woodcut, fig. 21, b. 

 Localities. — Caradoc or Bala Rocks of Shropshire and North Wales — everywhere; 

 Westmoreland; North and South Ireland, &c. Figs. 5 and 6 are the original speci- 

 mens of General Portlock's work ; and fig. 8 is the perfect young specimen given in the 

 ' Memoirs of the Geological Survey/ 



Foreign Localities. — Trenton Limestone of the United States, abundant (under the 

 name C. senaria). {Calymene. nivalis, Salter, is the representative species in the 

 Thibetan range of the Himalaya. See Col. Strachey's collection, now in the Mus. P. 

 Geology.) 



Calymene senaria. a is from 

 British Lower Silurian, a 

 cast, b from Ohio, with 

 the crust preserved. 



and Welsh Slate Rocks. 



Subspecies IT. 



Calymene Cambrensis, Salter. PI. IX, figs. 12 — 14. 



C. brevicapitata, Salter. Mem. Geol. Surv., vol. ii, pt. 1, pi. xi, figs. 3 — 5, 1848. 



C. brevicapitata, M'Coy. Pal. Foss. Woodw. Mus., pi. i r, figs. 4, 5, 1855. 



C. Blumenbachii, var. Cambrensis, Salter. Mem. Geol. Surv., vol. iii, pi. xvii, figs. 13, 14, 1865. 



C. modica, alutacea, fronte subrectd ; glabella vix trigond brevi trituberculatd. Cauda 

 axe angusto, lateribus valde arcuatis, multisulcalis, — sulcis profundi interlineatis. 



This marked species or subspecies has the glabella of the same shape with the Caradoc 

 fossil C. senaria, last described ; but is flatter, and the upper glabella-lobe is almost 

 obsolete. The front margin is produced, but not recurved. The body is elongate, and 

 not so convex as in C. brevicapitata, and the tail especially is more expanded, — its sides 

 less deflected and more arched, resembling in this respect our C. tuberculosa. The axis 



