PLATE 51. 
Fig. 1- 17. 607. 1. Apiocystites elegans. ( Pag. 243. 
1. The posterior side, showing the ovarian aperture, the shallow groove in which the arms are lodged, and 
the base of the larger tentaculum. 
2. The left side, showing the pectinated apertures and arrangement of plates on that side. 
3. The right side, showing the pectinated apertures and the protruding plates of the ovarian pyramid. 
4. The anterior side, showing the pectinated apertures at the base, the grooves for the anterior pair of arms, 
and the base of the large tentaculum at the summit. 
4 a. The base of fig. 4. 
5. Diagram showing the structure of one specimen having an intercalated quadrangular plate between the 
first and second series of plates. 
6. Diagram of the structure of another specimen, where there are only the usual number of plates in the first 
and second series. • 
7. A diagram of the structure of the upper part of a specimen where the arms are preserved. 
8. A part of the preceding diagram enlarged, showing the plates at the base of the arms, the position of the 
mouth, and anal pore in reference to the other parts. 
9. The brachial plates on the left side enlarged, showing the oral and anal orifices, with the bases of the two 
nearest tentacula. 
10. A part of one of the arms enlarged, showing the filament of ossicula running along the groove, and the 
base of the tentacula. 
11. A still farther enlargement, showing the first joints of the tentacula. 
12. A lateral view of the same. 
13. An enlargement of the ovarian pyramid and the surrounding plates. 
14. Profile of the same, showing the elevation of the pyramid. 
15. One of the pentagonal ovarian plates, with the three adjoining ones at the base, much enlarged. 
16. The pectinated plates of one of the higher pairs, showing the form and proportion of the two apertures. 
17. Another plate enlarged, to show the tuberculous character of the surface. 
Fig. 18, 19, 20. 608. 1. Hemicystites parasitica. ( Pag. 246.) 
18. An individual of the natural size. 
19. The plates of the ovarian pyramid enlarged, showing a double series. 
20. The specimen No. 18 enlarged, showing more distinctly the arrangement of the plates, arms, etc. 
Fig. 21, 22, 23. 609. 1. Palasastf-r niagarensis. ( Pag. 247.) 
21. The lower side of the specimen, of the natural size. 22. One of the arms enlarged. 
23. Several of the ossicula, with the short spines as they appear bordering the avenue. 
