PLATE 37.— Shell, etc. 



Figure 

 1 . Calcareous corpuscles of common-star-fish {Asterias ( Uraster) rubens), «, b, c, d, 



e ; /, the same from an Ophiura ; g, calcareous disk from an Echinus ; hj i, k, 



I, m, from an Ophiura (Echinodermata). 

 2*. Spine of an Ophiura ; 2, portion of the same more magnified. 



3. A pedicellaria of the common star-fish (Asterias rubens) ; on the right hand is 



a portion of the margin more magnified to show the teeth. 



4. Shell of Pinna, section parallel to the surface. 



5. Shell of Pinna, section perpendicular to the surface. 



6. Spine of an Echinus, transverse section. 6 a, segment of the same, more magnified. 



7. Sections of shell of a Terebratula ; a, perpendicular to, b, parallel with the 



surface. 



8. Portion of a sponge, with the spicula projecting from its surface. 



9. Shell of oyster, a, b, sections parallel to surface. 



10. Shell of oyster, showing the rhomboidal crystals of carbonate of lime, 



1 1 . Shell of oyster, showing the cellular appearance ; a, parallel with, b, perpendicular 



to the surface. 



12. Shell of hen's egg ; from a " soft " e^^. 



13. Shell of hen's egg, perfectly formed. 



14. Shell of egg of ostrich ; section parallel to surface. 



15. Shell of egg of ostrich ; section perpendicular to surface. 



16. Shell of lobster ; section perpendicular to surface. 



19. Anchor-shaped spicular hooks of Synapta (Echinodermata). 

 The remaining figures represent the spicula of sponges. 



a. Elongato-fusiform, tubercular, 



b. Acicular, acute at both ends. 



6*. Subulato-acicular, base trifid, rays shortly bifid. 



c. Subulato-acicular. 



d. Subulato-acicular, base swollen. 



e. iVrcuato-acicular, acute at both ends. 



f. Shortly cylindrical, ends doubly trifid. 



g. Subulato-acicular, base turbinate. 

 h. Subulato-acicular, base capitate. 

 i. Subulato-fusiform. 



k. Elongato-subulate, base capitate. 

 I. Terete, geniculate. 

 m. Filiform, ends capitate. 

 n. Acicular, ends bifurcate. 

 o. Acicular, ends trifurcate. 

 p. Subulato-acicular, base triradiate. 



q. Acicular, base tri-retro-cuspid. r. Uncinato-filiform. 



s. Bacilliform, ends tri-retro-cuspid. 



t. Arcuate, ends uncinate. u. Stellato-triradiate. 



V. Geminate, arms subulato-filiform, geniculate. 



w. Stellato-quadriradiate. x. Stellato-quinquiradiate. 



y. Stellato-multiradiate, ends capitate. 



a. Subulate, tuberculate. /3. Arcuate, spinulose, ends clavate. 



y. Stellate, insequiradiate. 



Z. Bacilliform, spinulose, with dentate, discoid, rotate ends, 

 e. Globular, with subulate spines. 



^. Oblong, with irregularly stellate ends, the rays capitate; '^ side view, X end view. 

 T]. Bacilliform, with stellate, rotate ends. 



