NIAGARA GROUP. 



239 



the second series is more numerous, and upon the upper angles of two of these the ovarian orifice 

 rests, its upper half occupying a depression in the base of a plate of the third series. The 

 upper pairs of pectinated apertures are likewise in part borne by two plates of the second series ; 

 while the five arms, which may be simple or subdivided, radiate from the apex, covering much 

 of the third and nearly all of the fourth series of plates. 



606. 1. CALLOCYSTITES JEWETTH {n. sp.). 



PL. L. Figs. 1 -11 ; and]2-I6 van? 



General form of body oblong ovoid, nearly symmetrical ; base composed of four plates, 

 one of which, bearing the pectinated aperture, is pentagonal, the second and fourth hexagonal, 

 and the third heptagonal. These plates support on their upper edges eight plates in the second 

 series, Nos. 5 and 6 of which are similar, and also 11 and 12, the others being of dissimilar form. 

 Of the basal plates. No. 1 is not directly opposite to the ovarian aperture ; but the position 

 of No. 6, bearing the second one of the lower pair of pectinated apertures, is almost directly- 

 opposite ; and a line drawn from this aperture, through) the centre of the base, to the lower 

 angle of plate No. 6, will divide the body into two parts of equal dimensions, though not 

 composed of similar parts. In the third series of plates, a single one is excavated on its lower 

 side, to form the upper margin of the ovarian aperture ; and two other plates bear the upper 

 member of the higher pairs of pectinated apertures. Above the apex of the pentagonal basal 

 plate, and resting upon the sloping edges of plates five and six in the second series, is a qua- 

 drangular plate marked 14 (fig. 11), its two higher sloping sides flanked by 13 and 15. This 

 is probably a supernumerary plate, not present in all individuals of the species. Every one of 

 these plates is more or less covered by the arms, which spread over the surface. The pectinated 

 apertures of the upper pairs are situated on each side of the ovarian aperture, and equidistant 

 from it, but not on opposite sides of the body. The individuals of the pair on the right side 

 are nearly horizontal in regard to each other, while those of the other pair are one above the 

 other, and the basal or anteal pair are nearly opposite the ovarian aperture. Arms double, or 

 composed of two parallel series of plates separated by a sinuated groove ; plates of the arms 

 of two forms, alternating ones similar, and opposite ones in the two series of different forms ; 

 fingers or tentacles composed of minute plates, articulating with the arms at the higher junction 

 of the larger and smaller joints and at the bottom of each sinus. Surface of the entire body 

 ornamented by polygonal depressions, having a more or less perfectly defined border and a 

 granulated surface. 



This is a most beautiful species, and, when furnished with tentacula and pedicel, was a 

 magnificent form. The base is large, gi'V'ing room for the strong attachment of a broad column ; 

 and the lower series of plates are expanded, with the exception of the pentagonal one, which 

 narrows this side, and gives to the whole body a more nearly straight anteal side, while the 

 posteal or ovarian side is swollen or pressed outward. The plates forming the ovarian pyramid 

 have not been observed j but from the character of the aperture remaining, we may fairly infer 



