36 



G. F. MATTHEW ON THE 



Head convex, semicircular or short, transverse, bordered all around, and having a 

 groove withiu the border, more or less emarginate in front. Grlabella sub cylindrical 

 ovate, or conical, distinctly lobed, generally touching the front border. Ocular fillets 

 oblique, extending back to the eyes. 



Fixed cheeks sloped downward in front of the ocular fillet, bent down outwardly 

 behind the eyes, having the posterior margin for the most part sinuate forward, with 

 the sides compressed. Eyes generally minute, placed in the middle of the cheeks, or more 

 toward the posterior margin, sometimes far distant [from each other?]. Facial suture 

 converging in front from the eyes, behind the eyes diverging more or less to the posterior 

 margin outward, obliquely sinuate deflexed. Exterior angles of the head, on account of 

 the posterior margin, for the most part are decidedly set forward ; they are produced in 

 short spines or very long arched ones. 



Thorax having the rachis for the most part narrow, and having grooved pleuras with 

 the inner part straight, short acuminate at the ends, or (especially in the posterior part of 

 the body) geniculated, and produced in very long reflexed spines. 



Pygidium small, entire or armed with little spines. 



Head moderately trans- 

 verse produced 

 at the 

 angles into short spines, 



Section I. | 



Pleurœ short, acuminate. Pygidium minute") Subgenus 



for ihe most part armed with short \ Leptoplastus 



spines, transverse. J (sens strict.) 



Section II. 



Pleur» in the posterior part of tlie body 1 



geniculated at the apex, reflected in long | : Subgenus 



spines. Pygidium small, entire (or?) fi Sphœropbthalmus. 

 longer. J I 



Head for the most 



part strongly 



transverse produced 



into long spines. 



Subgenus 

 Eu ry care 



Subgenus 

 Ctenopyge 



Of these four genera we have recognized in the St. John Basin only Leptoplastus and 

 Ctenopyge. The latter genus was originally confined by Linnarsson to four species, 

 C. peden, bmdcala, leretifrons and concava. To these under the classification given above 

 Dr. Brogger has added C. flagillifer and C. spectabilif. Representatives of these two species 

 have been found in the St. John Basin, and also imperfect remains that appear to belong 

 to C. peden. 



Ctenopyge flagillifer, Ang. var. (PI. XIII, figs 12 a and b.) 



ISôi—SphœroplUhalmwiJlaginifer, Ang. ' Pal. Scand.,' p. 4'J. Tab. xxvi, tig. 7. 



lS>^Q—Spha;rophthabnu>lJhlgiU>f^:r, Linrs. ' Forsteningarne med Peltura,' etc., p. 12- Tafl. i, figs. 13-17. 

 1882 — Ctennpgye flagillifer, Brog. ' Die Silurischen Etagen 2 und 3,' p. 120. Tab. ii, fig. 15 a, b, 16, 17. 



A. variety of this species occurs abundantly in some limestone lentiles of Division 3 b. 

 It is distinguished from the Swedish form, figured by Linnarsson in having no area 

 between the glabella and the anterior marginal fold, and from the Norwegian form 

 described by Brogger by the position of the genal spine on the movable cheek. In the 



