CTENOPYGE PECTEN. 85 



the first four or five segments are bent slightly downwards, rather broad (in the 

 direction of the axis), obliquely grooved; extremities produced into strong curved 

 spines, which in the anterior segments are more than half the length of the 

 pleurae and in the later segments become progressively longer and more curved 

 backwards. 



Dimensions. — Head and thorax about 12 mm. long. 



This form closely resembles Ct. hi sulcata but differs in several minor characters. 

 The eye is placed more forwards and further away from the glabella, and accord- 

 ingly the ocular ridge is more nearly at right angles to the axis, and the fixed 

 cheeks at the eye are wider. The glabellar furrows are decidedly oblique and are 

 not continuous across the middle line as they are in Ct. bisulcata, but in cleaved 

 rocks it is often difficult to determine whether there was original continuity or not. 

 The free cheeks are more distinctly angulate than in Ct. bisulcata, the cheek-spine 

 springs from a more forward point and at its origin is directed forwards. The 

 thorax is more uniform in width ; in Gt. bisulcata it begins to decrease rapidly 

 about the fifth segment, in Gt. falcifera not until the eighth. The axis is rather 

 narrower in the latter species, and the pleural spines are shorter and more falcate 

 in shape. The tenth segment is only shown imperfectly in our specimens, but the 

 axial ring is somewhat triangular and probably bore a median spine as in Ct. 

 bisulcata . 



The thorax and free cheeks are quite unlike those of Ct. pecten ; but the 

 cranidia of the two species are not markedly different. In Of. pecten, however, 

 the anterior margin is more strongly emarginate, in Ct. falcifera it is nearly 

 straight. In Ct. pecten the eye appears to be larger, extending as far forwards as 

 in Gt. falcifera, but also reaching further backwards. The posterior branch of the 

 facial suture in Ct. falcifera runs outwards from the eye and then curves back, 

 meeting the posterior margin at a considerable angle ; in Ct. pecten it seems to 

 run almost in a straight line outwards and slightly backwards, meeting the 

 posterior margin at a very acute angle. 



The wider fixed cheeks of Ct. directa and Ct. teretifrons serve at once to 

 distinguish those forms ; and the narrower thoracic axis and wider pleurae separate 

 Ct. expansa from the present species. 



Horizon and Localities. — Upper Lingula Flags: Malvern; Rhiwfelyn. 



4. Ctenopyge pecten (Salter). Plate IX, figs. 7—0; Plate X, figs. 1—7. 



1848. Olenus bi&ulcatus (pars), Phillips, Mem. Greol. Surv., vol. ii, pt. i, p. 55, fig. 2. 



1864. Olenus (Sphserophthalmus) pecten, Salter, Mem. Geol. Surv., Brit. Org. Rem., dee. xi, pt. viii, 



p. 9, pi. viii, fig. 12 ; not fig. 13. 

 1864. Olenus bisulcatvs (pars), Salter, loc. cit., pi. viii, fig. 6. 



