340 On ih< genus Pom/photyx and its Allies, 



Bhape, containing four or five otoeonites. The tentacles arc re- 

 tractile at the bases, but only slightly so near the extremities. 



Tic ova. These are laid on stones, shells, or the leaves of 

 plants. They are covered by a round, flattened, slightly tuber- 

 cnlate capsule of leathery consistence, quite insoluble in water. 

 alcohol, or glycerine. It is thin, brownish, and nearly transpa- 

 rent. These capsules are disk-like, and cover from five to ten 

 ova. placed in a single layer embedded in a brownish jelly. 

 Each ovum is contained in a transparent, tough, oval envelope. 

 Those which I have examined contain all stages, from the sim- 

 ple ovum to the embryo mollusk encased in a shell of a single 

 whorl, and with the eyes, tentacles, and viscera well advanced. 

 The first indication of organization is the separation of the vis- 

 ceral mass from the embryonic foot. The mantle, eyes, and 

 shell are developed early, lmt the tentacles only much later. 



The ova are deposited in the months of May and June. 



Notwithstanding the wide distribution and individual abun- 

 dance of the Pidmonata Lim/nophila, there are so few figures 



of the lingual dentition that it is difficult to arrive at a decision 



» 



in regard to the relatione of this singular form. The following 



are the character- of the principal genera which have been de- 

 finitely eliminated : 



L'nuiKKi {.shii/iidlis, jHihistr'is). 



Buccal plate arcuate, :ti><-\ anterior, nearlyjunooth. Two smooth 

 accessory lateral plates. 



Tentacles triangular flattened; eyes Bessile on their inner liases. 



< .. oitalia on the righl side. Fool bluntly rounded behind. 



Mantle margin simple, not extending beyond the orifice of the shell. 



<>\:i deposited in elongate cylindrical masses of jelly, withoul 

 perceptible em elope. 



Cusp of centra] tooth simply pointed, base bilobate. Inner late- 

 rals bicuspid, outer ones with more or less numerous notches. 



Shell spiral, turret <-<], dcxtral or ran-lv sinistral. 



I .//./ [gracilis), * 



