﻿9G 



SILURIAN TRILOBITES. 



a very thick old crust, and that partly accounts for the space between the glabella and 

 the front. In fig. 2 the crust is much thinner, and the space is consequently not so great. 

 But in both these the glabella reaches nearly to the front margin ; and is bell-shaped, not 

 triangular. In the species which follow, the glabella is more and more reduced in size, 

 till it reaches its minimum in the C. parvifrons, PI. IX, fig. 21 We shall take these 

 species in descending order. 



Localities. — Caradoc, Ireland (Prof. McCoy), Lower Llandovery, Carmarthenshire; 

 Radnorshire ; Pembrokeshire ; Mullock, Girvan, in Ayrshire j Mayhill Rocks of Norbury 

 and the Longmynd ; Malverns, &c. ; also Dingle, Ireland. Woolhope beds, Bogmine, 

 Shelve, Shropshire. Wenlock Shale and Wenlock Limestone, everywhere in 

 Great Britain and Ireland, where these rocks or their equivalents occur ; the chief speci- 

 mens from Dudley and Walsall. Lower and Upper Ludlow Rocks, Shropshire (rarely). 

 Marloes Bay, Pembrokeshire. Aymestry Limestone — Leintwardine (C. subdiademata, 

 McCoy). 



Foreign Distribution. — Sweden and Norway, in Upper Silurian. Niagara 

 Group of New York and Pennsylvania, &c. Mage U. Bohemia ; Barrande. (This last 

 locality is somewhat doubtful.) Kindred species are found all the world over in rocks of 

 Silurian age. 



C. Blumenbachii, var. CARACTACI. — Glabella angustiore breviore, caudd normali, axe 

 lato, laleribusque deflexis. PI. IX, figs. 3 — 5. 



[C. selene cep H ala, Greens Monogr. Cast No. 3, 1833?] 



C. subdiademata, M'Coy. Pal. Foss. Woodw. Mus. pi. i r, (fig. 10 only) ; 1855. 

 C. Blumenbachii, var. brevicapitata, in part. Salter in Mem. Geol. Survey, vol. 

 iii, pi. xvii, fig. 9 only, 1865. 



Not above 1^ inch long, and fully \\ broad, ovate, the head semicircular, with the 

 glabella equal in width to the cheeks, and in length rather greater than its breadth. 

 The glabella is parabolic, blunt in front, and has the three side-lobes well developed, — as in 

 the type-variety. The eye is rather forward, and there is no buttress opposite the middle 

 lobe. Except in this reduced size of the glabella, and in a slightly narrower axis and 

 more arched side-ribs to the tail, there is no essential distinction between it and the 

 ordinary form. It has been, however, occasionally (being always in the state of casts only, 

 confounded by myself and others with the true C. brevicapitata, which, indeed, being the 

 C. senaria of Conrad, the name had better be extinguished. I would call the present 

 variety Var. selenecephala, were I sure of Green's name ; but his cast is very imperfect. 



Locality. — Caradoc Rocks of Shropshire; abundant. (Mr. Edgell, Mr. Lightbody, 

 Geol. Surv. Collections, &c.) Bala, Llanwyddyn, Llangollen, Snowdon, &c, in N. Wales. 

 Desertcreat, Tyrone; Col. Portlock (Mus. Pract. Geology). Coniston, Westmoreland. 



Foreign localities. — North America, if C. selenecephala of Green be the same. 



