﻿252 BRITISH FOSSIL CRUSTACEA. 



Species 4.— CYCLUS HARKNESSI :— H. Woodw., 1870. PL XXXII, fig. 44 a, b. 



Cyclus Harknessi, H. Woodw., 1870. Geol. Mag., vol. vii, p. 556, woodcut ; 



and pi. xxiii, figs. 6 and 6 a. 

 — — H. Woodw., 1873. Brit. Assoc. Report, p. 304. 



This elegant form approaches most nearly to C. radialis, but the border of the shield 

 appears to be wanting. Its length is 3^- lines, breadth 3 lines, elevation 2 lines. Another 

 specimen measured 5 lines in length, 3| lines in breadth, and 3 lines in height. 



In this species the usual cervical furrow, dividing the anterior from the posterior 

 portion, is indicated by a ridge which commences in the middle of the shield where the 

 raised dorsal line, instead of terminating, diverges into two lateral branches directed 

 obliquely forwards, froming a Y-shaped elevation, from the branches of which the cervical 

 furrow is continued down to the latero-anterior border. 



Erom the margin of the dorsal ridge seven ribs take their rise on either side, and 

 descend the steep border of the buckler towards its rim, where, it is probable, they ter- 

 minate in rounded extremities as in Cyclus radialis (PL XXXII, fig. 43 b), but the matrix 

 conceals it (see fig. 44 <5). I have since been so fortunate as to detach a minute portion of 

 matrix from one of the specimens, and have satisfied myself that such is really the case, 

 so that to fig. 44 b a margin needs to be added along the basal line, as in the accom- 

 panying woodcut (fig. 81). The ribs are interrupted near the crown of the shield by 



Fig. 81. — Restored profile of Cyclus Harknessi, H. Woodw. 



two furrows, which encircle the posterior three-fourths of the buckler, so as to break up 

 the ribs near the summit into two sets of tubercles, the inner and upper series being the 

 larger and the lower series the smaller; the surface of the ribs is finely granulated. In 

 front, and partly enclosed by the Y" sna P e( i cervical ridge, and forming the top of the 

 anterior portion of the buckler, are four rounded lobes, with polygonal borders arranged 

 in a diamond-shaped pattern, the posterior one (cardiac ?) being the largest of the four. 



Placed around and forming a double border to these four lobes are eleven (?) others 

 arranged, firstly, five in one row, and secondly (along the outer margin), six. The 

 surface of the buckler is finely granulated. 



The three specimens found belonging to this species, which I have dedicated to my 

 friend Prof. Harkness, E.R.S., are all from the Carboniferous Limestone of Little Island, 

 Cork, from the collection of Mr. Joseph Wright, of Belfast. 



