Vol. 52.] OF THE CHALK ROCK. 93 



Family Aporrhaidse, Philippi. 



Genus Apoeehais, Da Costa, 1778. 



Subgenus Lispodesthes, White, 1875. 



Apoeehais (Lispodesthes) Mantelli, Gardner. 



1822. Bostellaria Parkinsoni, G. A. Mantell, ' Foss. S. Downs/ p. 108, pi. xviii. 

 f. 1, 2, 4-6, 10. 



1850. Aporrhais stenopterus, F. Dixon, 'Geol. Sussex,' p. 358 (p. 388, ed. 2), 

 pi. xxvii. f. 31, 36 ; 1854. J. Morris, ' Cat. Brit. Foss.' ed. 2, p. 235. 



1867. Aporrhais (Perissoptera) Parkinsoni, R. Tate, ' Geol. & Nat. Hist. Repert.' 

 vol. i. p. 99. 



1875. Aporrhais Mantelli, J. S. Gardner, Geol. Mag. dec. 2, vol. ii. p. 202, pi. vi. 

 f. 8, 9. 



EemarJcs. — The originals of Mantell's figures 1, 5, 6, and 10 are 

 in the British Museum. The specimens from the Chalk Eock are 

 in the form of casts only. 



Distribution. — Grey Chalk of Dover, Chalk Marl of Hamsey. 

 Chalk Rock of Cuckhamsley, and Luton cutting. 



Apoeehais, sp. 



Another species occurs in the Chalk Eock of Cuckhamsley 

 (Montagu Smith Collection), but is not sufficiently well represented 

 for determination. The spiral angle is about 20°. The whorls are 

 angular and provided with an almost median keel ; midway between 

 this and the anterior suture is a rib. No other ornamentation is 

 visible. 



Family Lampusidse, Newton. 



Genus Lahpusia, Schumacher, 1817. 

 Lampusia?, sp. (PI. IY. figs. 13, 14.) 



There are five specimens in the Montagu Smith Collection which 

 apparently belong to this genus — three are internal casts, one is an 

 external cast, and one has a small portion of the shell preserved. 

 The shell consists of five or six rather convex whorls, each with 

 about twelve prominent transverse ridges, and with numerous 

 longitudinal ribs of two sizes. The casts show the crenulation of 

 the outer lip. Spiral angle about 30°. 



Order Opisthobranchia. 



Family Eingiculidae, Meek. 

 Genus Avellaka, d'Orbigny, 1842 (sensu stricto). 

 Avellana, sp., cf. Humboldti, Miiller. (PL IV. fig. 15.) 



1851. Avellana Humboldti, J. Miiller, ' Mon. der Petref. der Aachener Kreide- 

 format.' part ii. p. 12, pi. iii. f. 15. 



1888. Ginulia Humboldti, E. Holzapfel, ' Die Mollusken der Aachener Kreide ' 

 (Palaeontographica, vol. xxxiv.), p. 84, pi. vi. f. 19-21. 



Description. — Shell globose, a little longer than broad, composed- 



