PLATE XIX 

 HOMCEOSPIRA EVAX Hall (Pages 3G0-365) 



See Plate XXII 



Figure 1. — Dorsal view of the youngest individual observed; having 

 a length of 1 nun. and a width of .8 mm. The ventral umbo is erect, 

 the foramen triangular and without deltidial plates ; the surface bears 

 two faint lines of growth, and outside the second of these are three fine 

 plications on each side of a median sinus. 



Figure 1«. • — Outline profile of the same ; showing the very shallow 

 valves. 



Figure 2. — Dorsal view of an average adult ; showing the characters 

 of advanced growth. 



Figure 2n. — Profile of the same. (2Sth Repl. N. Y. State Mas. Nat. 

 Hist., i± 25, figs. 14, IS.) 



Figure 3. — Dorsal view of an immature individual 5 mm. in length, 

 in which the plications on the earlier portion of the shell end abruptly at 

 a growth-line, from there outward the surface characters being altogether 

 primitive. 



Figure da. — Outline profile of the same. 



Figure 4. — The cardinal area in its earliest ol)served condition ; en- 

 larged from figure 1. 



Figure 5. — A later stage of growth in the cardinal area, the deltidial 

 plates having a considerable development. 



Figure 6. — A still later condition of this area, in which the plates 

 have united, enclosing the foramen. 



Figure 7. — The cardinal portions of an individual with an unusu- 

 ally elevated ventral umbo ; showing also an advance in growth from the 

 condition represented in figure 0. 



Figure 8. — The character of the cardinal area in a normal adult of 

 about the size represented in figure 2. The foramen has become circular, 

 and the ventral umbo so incurved as to conceal the deltidial plates. 



Figure 9. — A small obese example in which the foramen is almost 

 wholly concealed. 



II0:M(E0SPIRA SOBRINA sp. NOV. (Pages 3G6-3G9) 



Figure 10. — The youngest shell observed ; having a length of 2 mm. 

 and a width of 1.6 mm. The shell already bears two plications on each 

 side of the median sinus, and two mnch fainter elevated strias in the sinus 

 itself. 



