KISSURELLIDvE. 211 



to form in the adult a fissure in the trout edge of the shell ; in 

 young individuals, however, the foramen is entire. A. Adams. 



(I do not find it possible to distinguish satisfactorily the sub- 

 geneia " Subemarginula " and " Clypidina." The notch, upon 

 which the division principally depends, graduates from a great 

 depth in some species to being scarcely perceptible in others, but 

 no line of demarkalion can be drawn. In most species the depth 

 of notch depends on the age of the specimen, being deeper in the 

 young. 67. B. S.) 



1. planulata (pi. x. f. 1), A. Adams.— Elongato-ovalis, com- 

 planata, vertice subcentraii postice iuclinato, albida, costellis 

 radiantibus ajqualibus, imbricato-asperis lineisque concentricis 

 iucrementi decussata, basi arcuata ; apertune margine antice 

 valde inciso, incisura. lata et profunda. Ols. Anterior not so 

 short as in E. incisura. The slit much shorter and more 

 abrupt. 



2. incisura (pi. x. f. 2), A. Adams. — Elongato-ovalis, planu- 

 lata, pallide fulva, vertice antico retrorsum iuclinato, costellis in- 

 aiqualibus, radiantibus, longitudinalibus, imbricato-asperis, et 

 liueis elevatis, concentricis, decussata, basi arcuata, apertura} 

 margine crenulato, antice declinato, valde fissurato, incisura magna, 

 longa, baud usque ad verticem products, marginibus intus cal- 

 losis. 06s. In this species the slit is long, and a half-cut conti- 

 nuation of it extends to the apex. This is, unfortunately, not 

 fully shown in the figure. 



3. clypkus (pi. x. f. 3), A. Adams. — Elongato-elliptica, valde 

 depressa, testacea, macula luteola in medio dorsi, vertice subcen- 

 traii, postice iuclinato, costis confertis, aequalibus, radiantibus, 

 imbricato-asperis, ornata, basi arcuata ; aperturae margiue crenu- 

 lato, antice valde fissurato, fissura magna, apertura intus bimacu- 

 losa. 06s. Narrow, scabrous, and has some prominent ribs. 



4>. Huzardi (pi. x. f. 4), Payr. — Ovalis, patelliformis, valde 

 depressa, alba, vertice subcentraii, brevi, leviter reflexo ; costellis 

 longitudinalibus numerosis minoribusque interpositis; striis 

 transversis ; margine crenulato. 06s. Very depressed, beauti- 

 fully cancellated, with posterior end short. 



5. dilecta (pi. x. f. 5), A. Adams. — Elongato-ovalis, sub- 

 quadrangularis, alba, valde depressa, vertice subpostico, retror- 

 sum declinato, costis subdistantibus, radiantibus, asperulatis, et 

 liris elevatis, concentricis, pulcherrime cancellata, basi arcuata; 

 apertura: margine denticulato, antice valde fissurato. Obs. More 



