2 



BRITISH FOSSILS. 



genus from the materials already acquired, rather than to wait for 

 the chance of finding a perfect specimen. 



M. Corda, in his voluminous but most inaccurate work, has given 

 a drawing of this genus under the name of Cyclopygey* in which the 

 large reticulated eyes are mistaken for a granulated glabella, and the 

 facial suture made to travel through the middle of them ! 



Description. — The head is three lines long by about four wide, 

 very gibbous, almost as deep as broad. The. glabella is of a parabolic 

 form, and projects forwards beyond the eyes so as to break the oval 

 contour of the head ; behind it invades the neck segment, and almost 

 obliterates it, leaving only a small portion on each side, which is 

 separated from the glabella by a rather strong furrow. Lobes none, 

 but a short oblique oval indentation on each side occurs at about the 

 lower third of the glabella, the pair of indents being placed as far 

 from the sides as from each other ; a gentle swelling occurs beneath 

 each impression. Some transverse arched striae run across the base 

 of the glabella, which otherwise appears to be smooth. Eyes very 

 large, and occupying every part df the cheek except the lower inner 

 angle ; they are very conve:^, and bent round towards the under 

 surface on the sides ; they are still more convex in front, where the 

 two eyes meet and coalesce along a median line, and are there over- 

 hung by the gibbous point of the glabella ; they occupy, therefore, 

 the entire length of the facial suture, and quite shut out the usual 

 anterior margin. When the head is viewed on the under side, there 

 is a short triangular space (see fig. 7, b) unoccupied by the lenses, 

 which is a prolongation of the rostral portion ; but except this small 

 space, and the lower comer before mentioned, there is nothing to be 

 seen of the anterior segment but that portion which is on the lower 

 surface. It is not very easy to reckon the number of lenses in the 

 eye, but they are rather large in comparison with Asaphus or 

 Illoenus, and there are not more than 1,100 or 1,200 in each eye. 

 They were probably convex externally (as in Phacops and 

 Cheirurus), and not covered up by a level cornea ; when they have 

 fallen out, concave pits with prominent interspaces are left upon 

 the cast of the inner surface. The facial suture must of necessity 

 follow the outline of the glabella in this species, and accordingly we 

 have one specimen in which the cheeks, that is the eyes, are absent, 

 and a thin rim only surrounds the glabella. At its posterior ter- 

 mination, however, this suture leaves the inner and lower angle of 



* Prodrome Monogr. Bohui. Trilob. (1847), f. 32. {^Cyclopyge megacephala, Corda. 

 j^gle rediviva, Barr.) 



