Mi*. W. H. Benson on a new Species of Helix. 175 



Fig. 15. The same, with one division of the spore abortive. 



Fig. 16*. The same. Sporangial frustule surmised to be of the size pro- 

 duced by these conjugations. In all these frustules the spe- 

 cific characters are too small to be delineated on the scale to 

 which they are drawn, although perfectly distinct under the 

 microscope. 



Fig. 17. Pinnularia gibba, Ehr. In conjugation. The pellicle of the 

 gelatinous secretion and the ends of the capsules absent. 



Fig. 18. The same ; more advanced stage. The valves of one of the con- 

 jugating frustules absent. 



Fig. ID. The same. Relative size and form of conjugating frustule. 



Fig. 20. The same. Full size of sheath of sporangial frustule in this 

 gathering. 



Fig. 21. The same. Full size of frustule produced hy these conjugations. 



XIX. — Description of Helix odontophora, a new Species of the 

 Corilla type, from Upper Ouvah, in Ceylon. By W. H. Ben- 

 son, Esq. 



Helix odontophora, mihi, n. sp. 



II. testa late umbilicata, rotundato- vel ovato-discoidea, solidula, 

 castanea vel rufescenti-lutea, superne subplanulata, oblique 

 tenuiter costulato-striata, subtus valde concava, striata, nitida ; 

 spira planiuscula, versus apicem obtusum elevatiore, sutura im- 

 pressa ; anfractibus 4, primis convexiusculis, ultimo antice con- 

 vexiore, turn descendente, dilatato-defiexo, subtus valde inflato; 

 apertura perobliqua, obtuse subcordata, lamellis 2 parietalibus 

 (superiore longe intrante curvata, inferiore subparallela, breviore, 

 subcurvata, ab apertura remotiuscula), palatalibus 4 brevibus 

 semilunaribus vel sinuatis (omnibus integris ab apertura conspicuis, 

 extus perlucentibus) coarctata ; peristomate purpurascenti-albido 

 vel castaneo, calloso, breviter reflexo, margiuibus superiore et in- 

 feriore subdentato-incrassatis. 



Diam. major 26, minor 19, alt. 8 mill. 

 22, „ 17, „ 7 „ 



Habitat in montibus Ceylanicis prope Fort M 'Donald, Bandarewella, 

 et Bibiligamua ad altitudinem ped. 4500. Teste Dom. F. Layard. 



The examination of a broken specimen of a shell, supposed 

 to be H. erronea, which I received from Mr. F. Layard, with the 

 internal lamellse fully exhibited, convinced me that a peculiar 

 type had been overlooked ; and Mr. Layard kindly forwarded to 

 me the shells which he referred to H. erronea from Upper Ouvah 

 and Pusilawe : the latter all belong to the true erronea type, 

 with three parietal and four lengthened palatal lamellse, also a 

 single specimen out of five from Bandarewella ; the rest all 

 prove to be H. odontophora, with only two parietal lamellse and 

 more delicate sculpture (as in H. Anax, mihi, and H. Hnmberti, 

 Brot), only four whorls, and short semilunar or sinuate palatal 

 lamellse entirely visible from the aperture, — the Fort M 'Donald 



