CAMAROTCECIIIA ACINUS Hall (Paces 339-341) 



Figure 9. — Ventral view of a young shell in a secondary stage of 

 growth ; showing a single growth-line and the embryonal median ridgt'. 



FiGUuic 'J(t. — Dorsal view of the same. The foramen is slightly nar- 

 rowed, but without evidence of deltidial plates ; the embryonal sinus is 

 well defined. 



Figure '.th. — ( Outline profile of the same. 



FiGuni-: 10. — \'entral view of a specimen 3.25 mm. in length. 



Figure 10a. — Dorsal view of the same. The mature fold and sinus 

 have not yet begun to develop ; the foramen shows increased constriction 

 at its base, and slightly thickened niargins. 



Fkure loll. — Outline piotile of the same. 



Fici'RE 11. — Dorsal view of an average adult, x 1- 



FiGURK 11a. — ri'ulile of the same. 



FiGuiiF, 116. — Front view of the same; showing the elevation of the 

 median fold. 



FJIYNCTIOTUET.V CUXEATA Dalma.v, var. AMEIIICANA 

 Hall (Pauics 3."i1-35U) 



See Plate XXH 



Figure 12. — Dorsal view of a shell represmiting the eai'liest stage of 

 L;ro\vth observed ; length l.Snini. The foramen is widely triangular and 

 unolistructed, the surface is covei'ed with all the plications of maturity, 

 and the sub-ch-cular valve l)ears a broad median depression. 



Figure 12((. — Outline profile of tiie same. 



FiGUitE 13. — Similar view of a shell 3 mm. in length. The outline 

 has become elongate, the foramen narrowed, and its margins thickened. 



Figure 13a. — Oatline [irofile of the same. 



Figure 14. — Dorsal view of a normal adult individual; showing tlie 

 elevated beak and broad plications. Natural size. 



Figure 14((. — Profile of the same; showing the elevation of the dor- 

 sal fold. 



Figure 146. — Front view of the same. (28;/; Hept. X. V. Slate .Ifus. 

 Nat. Hist., pi. 2.1, figs. 31, 34, 30.) 



Figure 1.5. — .V series of outlines of flie anterior margin ; showing 

 the embryonal sinus or depression in the dorsal valve in young forms, 

 reaching its maximum in individuals having a length of 4. .5, and becom- 

 ing obsolete, or the line of junction .straight, in .specimens 7 mm. in 

 length. Outline (i shows the inception of the dorsal fold. In 8 the four 

 median plications are distinctly elevated ; 9 is from a normal full-grown 

 individual, and 10 represents the maximum elevation of the fold. The 

 outlines, except in 9 and 10, are enlarged to the diameter of a fully 

 developed specimen. 



Figure 10. — Cardinal area of figure 12. 



Figuuk lOrt. — Outline profile of the same. 



