TRILOBITES OF THE UPPER SILURIAN ROCKS. 



653 



shape of the caudal portion, this fossil is clearly of the genus Homalonotus, and approaches 

 very nearly to our English species. This is the only foreign specimen figured in this work, 

 and I have selected it, because it marks the fact, that the eminent astronomer, after whom 

 it is named, occupied a portion of the time he passed in Southern Africa in promoting geo- 

 logical investigation. The fossil was first sent to me by him. It occurs in the range of the 

 Cedar Mountains (Cedar-berg), N. of the Cape colony, where it is associated with other tri- 

 lobites, one of which is undistinguishable from Calymene Blumenbachii, while another ap- 

 proaches very near to C. Tristani, and also with certain inoilusks, which leave no doubt of 

 the existence in that region of rocks of the same age as our Upper Silurian 3 namely, Cucullaa 

 ovata, PI. 3. f. 12 b., (passage-beds from the Old Red Sandstone), Orbicula rugataf, Conularia 

 quadrisulcata, Leptcena lata, with fragments of Turbo, Turritella, Crinoidea, and a new 

 species of Nucula, which ought to be named N. Smithii, in honour of Dr. Smith, the naturalist 

 and explorer of South Africa, who collected the specimens h 



Calymene, Brongniart. 



Gen. Char. — -"Corps contractile en sphere presque hemicylindrique. B ouclie r port an t p lusieurs 

 tubercules ou plis, deux tubercules oculiformes reticule's. Abdomen et post abdomen a bords 

 entiers, V abdomen divis£ en douze ou quatorze articles. Point de queue prolong^e." 



Calymene Blumenbachii, figs. 5, 6 and 7- (Brongn. PI. 1. f. 1.) Syn. Dudley fossil, Entomolithus 

 paradoxus, Blum. 



" Clypeo rotundato, tuberculis sex distinctis in fronte ; oculis in genis eminentissimis ; corpore 

 tuber culato.'" 



This species has six rounded protuberances on each side of the central lobe of the head, and 

 fourteen articulations in the back. The tail is small, (see f. 7-)> and the shell is covered with 

 little round tubercles of unequal size. It may be added that the Calymene Blumenbachii 

 generally exhibits a sculpture of the segments somewhat similar to that described in Homalo- 

 notus, and also has often the appearance of being marked by a row of rather wide, slightly raised, 

 tubercles on each side of the central lobe of the body (one at the end of each rib.). In PI. 1. f. 1 c. 

 of Brongniart, these costal protuberances appear rather as the raised or bent ends of the central 

 segments. In examining a great number of specimens, we find that this feature, though so 

 strongly apparent in our f. 5., is very inconstant ; for we detect numerous gradations between the 

 apparently distinct tuberculatum in f. 5. and those which are entirely free from it, like f. 6. As 

 the appearance of such tuberculations is most apparent in those specimens which have been 

 coiled up, and is not visible in those which are straight and unfolded, may we hazard a con- 

 jecture that the swellings or knots in question are to a great extent the result of torsion and 

 lateral pressure ? 



Loc. Ludlow, Dudley, 8$c, The splendid specimen, f. 6., is in the cabinet of Mrs. Downing 

 of the Priory, Dudley. The smaller forms, (those usually found), figs. 5 and 7 ? are from the 

 Wenlock Shale of Burrington, near Ludlow, where they were collected by the Rev. T. T. 

 Lewis and myself. 



The Calymene Blumenbachii occurs both in the Ludlow and Wenlock formations, but most 



1 In the first part of the 8th vol. of the Journal of the Geographical Society just published, Capt. Alexander 

 thus alludes to the Cedar Mountains :- — " The principal rock of the higher parts (5000 feet), appears to be an 

 ash-coloured, quartzose sandstone ; the secondary range contains many marine petrifactions, shells and fish, at 

 a height of 2000 feet above the sea." — p, 3. 



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