5 lines 



or 10 mill. 



2 1 



)> 5 ?> 



6i „ 



>» 13 ,, 



2i 



j> & >> 



BELLINURUS ARCUATUS. 241 



of its various body-segments into long spines spreading out on each side of 

 the body, and gradually decreasing as they approach the tail, from which proceeds an 

 enormous spine. These characters sufficiently distinguish it from any other species. 

 The head and body in the specimen figured appear to have been a little squeezed 

 together. Another specimen of what I believe to be the same species, obtained by Mr. 

 John Edge, is still more perfect, with the exception of the tail-spine, a portion of which 

 has been broken away ; it shows a slight wrinkling or furrowing of the expanded margin 

 of the cephalic shield, as well as the sulcated pleurae and single tubercle upon each ring 

 of the axis terminating in a larger and more obtuse prominence on the tail. The spine 

 or telson which is attached to this portion exhibits a central longitudinal ridge, having 

 a membranous expansion on each side, similar to that noticed by Parkinson as occurring 

 in the species described by Martin, and which I have referred to B. belhdus, Konig. 

 "The following are the measurements of fig. 1 a: 



Length from anterior margin of cephalic shield to end of tail 



Length from anterior to posterior margin of cephalic shield . 



Breadth of cephalic shield .... 



Length of body and tail .... 



Breadth of body at cephalic shield . . . 4 „ „ 8 ,, 



" Measurement of fig. 1 c : 



Total length from anterior margin of cephalic shield 



to point of telson . . . .1 inch 1 line or 27 mill. 



Breadth at widest part of spines . . 7 lines „ 15 „ 



Breadth of cephalic shield . . . 5, ,,,10,, 



Length of telson . . . . 10 ,, „ 20 „ : 



Locality. — From Coal-shale, Bilboa Colliery, Queen's County. 



Species 4.— BELLINURUS ARCUATUS :— Baily, 1863. PI. XXXI, figs. 2 a, b. 



Bellintjrus abcuatus, Baily, 1863. Ann. and Mag. Nat. Hist., 3rd series, vol. xi, 



pi. v, fig. 2 a — c. 



" General form broadly ovate, acuminate posteriorly ; axis convex. Cephalic shield 

 semicircular, slightly elevated, declining towards the circumference, and surrounded by a 

 narrow, flattened margin, the central portion or glabella having three ridges extending 

 to about two thirds the breadth of the shield, rounded at their anterior extremity, and 

 forming a double arch, the central portion being broadest at its posterior extremity, the 

 two outermost ridges curving at about half their length towards the very slightly raised 

 semicircular eyes, and continuing beyond the posterior extremity of the shield in two 

 sharp straight spines, which project over the body about one tenth of an inch; the 



