13 



species ; and are formed in the sutures by the two adjoining 

 plates. Surface thickly pitted, giving it an undulose appearance; 

 and many of the plates have faint radiating ridges proceeding 

 from the center of the base in the basals, and from the center of 

 the others towards the angles. Basal plates four, large, one pen- 

 tagonal, one heptagonal, and two hexagonal ; second series eight, 

 one heptagonal, three hexagonal, and four pentagonal ; third 

 series six, three heptagonal, and three hexagonal ; intercalated 

 plate between second and third series quadrangular ; the plates 

 surrounding the intercalated plate are short in the second series 

 and long in the third ; the reverse of this is observed on the op- 

 posite side, where the plates of the second series supporting the 

 " anal aperture " and the two upper hydrospires are long, and 

 the third series immediately above are correspondingly short. 

 Hydrospires placed as follows : one between the basal plate, di- 

 rectly beneath, and the plate of the second series to the left of 

 the intercalated plate ; the two others are supported on the right 

 upper margins of the two plates of the second series on either 

 side of the two supporting the " anal aperture ;" and the opposite 

 plates of the third series above ; they are semi-oval in outline, 

 and have strongly reflexed projecting lips, except on the basal 

 side of the lower one, where it is on a level with the surface of 

 the plate ; they are crossed by ten or twelve bars ; each plate 

 bearing a part ; these are at right angles to the sutures which 

 divide them. 



"Anal" aperture large, supported by two plates of the second 

 series, and capped by one of the third. Arms five, extending 

 over half-way down over the second series ; the two to the right 

 of the intercalated plate slightly bifid at their lower extremity ; 

 they are furnished with a central groove, and are composed of 

 two irregularly alternating series of plates. Tentacula composed 

 of small, slightly rounded joints. 



The apex has been weathered out of the only specimen seen. 

 From the middle part of the shale. 



While this species agrees with C. jewettii in the number of arms, 

 the relative position of the hydrospires, and the number and ar- 



