NIAGARA GUOUP. 241 



Fig. 2. The right side, showing the pectinated apertures. 



Fig. 3. The anterior side, showing the pectinated apertures near the base, and the position of 

 the intercalated quadrangular plate. 



Fig. 4. View of the base, showing the large foramen opening from the column. 



Fig. 5. A portion of the base of the arm-plates on the left side, showing an aperture marked a, 

 which may be the mouth, and another pore-like orifice which is perhaps the anal 

 pore. The little oblong body marked t is the porous tubercle, which is very distinct, 

 and of a texture different from the plates to which it is attached. The bases of tenta- 

 cula are marked b h. 



Fig. 6. Two plates from the right side of the body, enlarged, showing the relative form and 

 proportions of the pectinated apertures. 



Fig. 7. One of these pectinated apertures still farther enlarged, and defining more clearly the 

 transverse bars and the spaces between. 



Fig. 8. A portion of the surface enlarged, showing the polygonal spaces, which are separated 

 by scarcely elevated ridges. 



Fig. 9. The structure and arrangement of the arms and plates composing them, with the relative 

 position of the simple and dichotomous ones ; the originating points of the tentacula, 

 with the relation of the whole to the ovarian and pectinated apertures, the oral 

 orifice, etc. 



Fig. 10. The bases of the arms enlarged, showing more distinctly the oral orifice and tubercle 

 on the lower one, which is larger than the others ; and also that from right to left 

 there is a continuous line, marking the direction of the anterior and posterior sides. 



Fig. 11. The structure of the body, including the first and second series of plates, and a part of 

 the third series. 



Fig. 12. An individual having a slightly different form, being more contracted towards the apex, 

 but in other respects having the same arrangement of parts, surface marking and 

 other details, with the exception of the arms, which are simple throughout their 

 whole extent. The anal orifice holds the same position, but the part immediately 

 above this is mutilated. A portion of the column still remains attached, the joints of 

 which are compressed, carinated, and somewhat reflexed. 



Fig. 13. The arms spread out in a plane, and showing their relation to the ovarian and pectinated 

 apertures. 



Fig. 14. Section of the column, showing the large canal. 



Fig. 15. A portion of one of the arms enlarged, showing the sinuated groove, with the bases 

 of tentacula marked b b. 



Fig. 16. The granulated surface of the plates of the arm magnified. 



Fig. 17. A fragment of a column very similar to that attached to the body fig. 12. 



Fig. 18, An enlargement of the same, showing the crenulated edges of the joints. 



[Pal^ontolosy — Vol. II.] 31 



