1881.] NATURAL SCIENCES OP PHILADELPHIA. 413 



Fig. 2. Strotocrimis subumbrosus Hall. Half of one ray, showing the 

 mode of branching. The medium lines indicate the course of the 

 radial ridges at the surface of the plates. 



Fig. 3. Steganocrinus sculptus Hall. Showing the free rays and the lateral 



arms. 

 Fig. 4. Side view of a portion of a free ray in Steganocr. sculptus, 



showing the ventral covering, and the position of arm openings and 



respiratory pores. 



Fig. 5. Transverse section of the same, showing the form of the inner 

 passage. 



Fig. 6. Reteocrinus Bichardsoni "Wetherby. A part of one of the rays 

 within the calyx, showing the fixation of pinnules by means of inter- 

 calated plates. 



Fig. 7. Eucladocrinus millebrachiatus W. and Sp. Ventral side of body, 

 with free rays and lateral arms. 



Fig. 8. Showing the position of the apical dome plates in Batocrinus 

 pyriformis, a species with a large, almost central anal tube. 



Fig. 9. Arrangement of plates in the dome of Agaricocrinui. 



Fig. 10. Apical dome plates of Steganocrinus sculptus. 



EXPLANATION OF PLATE 19. 



Fig. 1. Vault of Ollacrinus tuberosus L. and C, showing the five de- 

 pressed, oval-shaped groups of small plates opposite the interradial 

 appendages. 



Fig. 2. Batocrinus discoideus, showing the plates in the calyx. The 

 adjoining plates of the dome added to show the exact position of ann 

 openings and respiratory pores. (The pores are not visible where the 

 arms are attached, but here figured to point out their position.) 



Fig. 3. Ventral covering of Oranatocrinus Sayi, showing the apical and 

 other dome plates, also the extension of this covering over the ambu- 

 lacral furrows. (O = so-called ovarian openings, f = forked plate, 

 d = deltoid pieces. ) 



Fig. 4. Batocrinus discoideus Hall. Horizontal section through the arm 

 openings and respiratory pores, exposing their passages through the 

 test. 



Fig. 5. Natural cast of Physetocrinus ventrieosus, showing the position of 

 certain poi-es or pits upon the inner floor of the vault, represented in 

 the cast as small cones. 



Fig. 6. Cross-section at midway of Oranatocrinus Norwoodi Shumard. 

 Showing the hydrospires. [l = lancet piece ; AQ ^ ambulacral and 

 food passage.) 



