91 



rhombs are on a line with the mouth, the lower close to the base. These 

 rhombs are not double, (as they are in A. elegans, Hall), but single, 

 i. e., the two triangles, of which each is composed, have their bases in 

 contact, the elongated pores being continuous across the suture between 

 the two plates on which each rhomb is situated. Regarding the side in 

 which the mouth is placed as anterior, and the interbrachial spaces on 

 each side of and next to it as the right and left sides, the rhombs are thus 

 disposed : — the left hand rhomb has its longer diagonal extending 

 obliquely downwards and backwards, at an angle of about 30° with the axis 

 of the fossil : — the right rhomb has its longer diagonal very nearly at right 

 angles to the axis : — the basal rhomb is mostly situated in the posterior 

 interbrachial space on the left hand side and slopes downwards and back 

 wards at an angle of about 45°, its lower angle passing under the third 

 arm from the mouth. The arms are grooved along the middle, and have 

 four or five pinnulge on each side. The surface is covered with irregular 

 elevated lines which in some places unite so as to inclose small poly- 

 gonal spaces, giving to such parts a pitted aspect. Length, 7 lines; 

 greatest diameter about 4J fines. Only one specimen has been collected. 

 A. elegans, Hall, has only four arms and the two halves of the rhombs 

 separated. Grimsby; Niagara formation. J. Pettit. 



Fig. 28. — Apiocystites Huronensis. A specimen partly buried in stone. 



A. Huronensis, n. sp. — The specimen is partly buried in stone and 

 its generic characters cannot be ascertained. The plates are moderately 

 convex, depressed at the sutures. The rhomb at the base is one-half on 

 a basal plate, and one-half on a plate of the second series. In the upper 

 part is another rhomb, one-half of which is on a plate of the third series, 

 and the other apparently on a plate of the fourth. The lower half, how- 

 ever, of the basal rhomb, and the upper half of the upper rhomb are not 

 distinctly seen. As no arms are visible, it seems certain that this species 

 is not a true Ajnocystites. The position of the rhombs also favours this 

 view. The specimen was found near Cabot's Head, on the shore of Lake 

 Huron. Clinton ; or Niagara formation. A. Murray, Esq. 



A ? Tecumseth, n. sp. — This name is proposed for a Cystidean collected 

 by Prof. R. Bell and H. G. Vennor, on Manitoulin Island in 1865. Only" 

 detached plates and fragments of the column were found. Most of the 



