PLATE XVIII 



CAMAROTCECIIIA WIIITII Ilui. (Pages 3U-346) 



FiGUKK 1. — The earliest observed stage of growth, the sliell measur- 

 iiig 2.75 mm. in length by 2 mm. in width. The deltidial plate.s liave 

 already begun to form along the edges of the triangular foramen, and 

 four pairs of plications are visible on the dorsal valve. 



FiGUUE la. — Outline profile of the same. 



Figure 2. — Dorsal view of a norn)ul adult having two plications on 

 the fold. Natural size. 



Figure 2a. — Profile of the same. 



Figure 2?j. — Front view of the same. (28//j liept. N. Y. State A/ us. 

 Nat. Hist., pi. 2G, figs. 23, 20, 25.) 



Figure 4. — The cardinal features of a young example with a length 

 of 3.25 mm. ; showing the inception of the deltidial plates. 



Figure 4a. — Profile of the same. 



Figure 5. — Cardinal features of an individual which has attained a 

 length of 6 mm. The imibo has become incurved and the development 

 of the plates is well advanced, but it is arrested at this stage, the foramen 

 not becoming enclosed at maturity. 



Figure oa. — Outline profile of the same. 



CAMAROTCECHTA NECiLEC'TA Hali. (P.vge 341-314) 



Figure 6. — Dorsal view of the youngest shell observed; luuing a 

 length of .7') mm., and a width of .5 mm. Though the foramen is open 

 and without evidence of thickenc'd margins, four fine plications have 

 already appeared on tlie dorsal valve. 



Figure da. — Outline profile of the same. 



Figure 7. — Dorsal view of an individual with a length of 2.25 mm. 

 The deltidial plates are in an incipient condition and the plications of 

 the surface have considerably increased. 



Figure 7a. — Outline profile of the same. 



Figure 8. — Dorsal view of a mature example. Natural size. 



Figure 8a. — The same in profile. (2Sth llept. N. Y. State Mus. Nat. 

 Hist., pi. 20, figs. 3, 5.) 



Figure 3. — A somewhat abnormal adult, having tim^e ])licati()ns on 

 the fold and the lateral plications obsolescent. X 2. (ll//t Ann. Rcpt. 

 Geol. Surv. Incl., pi. 27, fig. 3.) 



