404 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



extreme width of the glabella ; the eyehd is tubercular, and the len- 

 tiferous surface smooth. 



The triangular cheeks are produced backwards, their extremities 

 terminating in prolonged spines. 



The neck-furrow is continuous ; and the strong neck-lobe, broad- 

 est in the centre, is smooth, but has a tubercle at each extremity. 



Hypostome ovate, rhomboidal, subtrilobed, tubercular, and sur- 

 rounded by a sinuated border ; its convex extremity very broad, and 

 its cucullated tip abuts against a large tubercle placed upon the an- 

 terior margin of the head (PL XXXII. fig. la). 



Thorax of eleven rings, its convex axis or central division some- 

 what narrower than the pleura?, and separated from them by deep 

 axal furrows. Two tubercles occur upon each of the axal segments, 

 one at each end. A spine is placed upon the seventh, and another 

 upon the tenth segment of the axis. 



The pleurae, usually covered with small tubercles, are horizontal 

 halfway, then strongly curved downwards, and slightly bent back- 

 wards ; their edges sharpened in front, and their terminations bifid 

 or notched, and tubercular. 



Tail long and acutely triangular, terminated in an extended mucro ; 

 its axis, tapering backwards to its acute termination, is of less width 

 than the lateral parts, and is composed of about thirty distinct rings. 

 Its centre is smooth and has about seven tubercles prominent and 

 distinct, four rings intervening between two tubercles. The articula- 

 ting edge is broad. 



Eight strong ribs on each side gradually decrease in size as they 

 approach the caudal termination, the anterior ones curving back- 

 wards ; they are separated by deep furrows, and a distinct tubercle is 

 placed upon the upper and inner end of each. 



Cybele variolaris, Brongniart, sp. Pl. XXXII. figs. 6-10. 



This species is figured in the * Silurian System,' where it is inad- 

 vertently represented as having thirteen body-rings*. Burmeister 

 being unacquainted with the form, and misled by the inaccuracy of 

 the figure above referred to, was induced to consider it as a Calymene, 



Synonyms, — Calymene variolaris^ Al. Brongniart, 1822, Crust. 



Foss. tab. 1. fig. 3 B. 

 Calymene variolaris, Murch. Sil. Syst. 655, pl. 14. fig. 1. 

 Phacops variolaris, Emmerich, Trilob. i. 20. 4. 



A description of this species having been given by my friend Mr. 

 Salter in the * Memoirs of the Geological Survey,' vol. ii. part 1 . 

 p. 344, it will be sufficient to notice its chief points of difference from 

 that last described. 



The cephalic shield and thorax have a general similarity to those 

 of the preceding species ; but the glabella is rather mope prominent 



* A recent inspection of the specimen figured by Sir R. I. Murchison from the 

 cabinet of Mrs. Downing, of the Priory near Dudley, enables me to state that it has 

 eleven body-segments. 



