PLATE XIX 

 IIOMCEOSI'IRA EVAX Hall (Pagks :ii;()-:3(;5) 



Sue Plate XXII 



Fi(iUi:F. 1. — Dorsal viewol tlie youngest individual observed; having 

 a length of 1 mm. and a width of .8 mm. The ventral und]o is erect, 

 the foramen triangular and ^vitllout deltidial plates; the surface bears 

 two faint lines of growth, and outside the second of these ai'e three fine 

 plications on eaeh side of a nu'dian simis. 



FKiUKio 1(1. — Outline profile of the same ; showing the very shallow 

 val\'es. 



FiiifRB 1'. — Doi'sal view of an average adult ; showing the cliaraoters 

 of advanceil growth. 



FlGOiiE !'<;. — Profile of the same. {'2^lh Rept. N'. Y. Stale Mns. A"<il. 

 Jlisl., 1,1 25, tigs. 14, IS.) 



FiGUUE 3. — Dorsal view of an immature individual .5 mm. in lengtli, 

 in which the plications on tlie earliei- portion of the' shell end abruptly at 

 a growtlidine, from there outward the surface characters lieing altogether 

 primitive. 



FioDEE "(/. — Outline profile of the same. 



Figure 1. — The cardinal area in its eailiest observed condition ; en- 

 larged from figure' 1. 



FiGUKE tj. — A later stage of growth in the cardinal area, the deltidial 

 plates having a considei'alile development. 



FiGGKE li. — A still later condition of tliis area, in which the plates 

 have united, enclosing the foramen. 



Fjguuk 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 figuii' 0. 



FiGTiiE H. — 'l"he character of tire 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 0. — A small ohese example in which the foramen is almost 

 wholly concealed. 



IIOi\I(FOSPIP.A SOBPJNA sp. nov. (Pages 308-369) 



FiGUP.K 10. — The youngest shell observed ; having a length of '2 mm. 

 and a width of 1.6 mm. Tlie shell already bears two ]ilications on each 

 side of the median sinus, and two much fainter elevated stria' in the sinus 

 itself. 



