400 J. Starhie Gardner — On Cretaceous Aporrha'idce. 



two keels of nearly equal prominence, striated between. Wing 

 simple, long, narrow, awl-shaped ; aperture narrow ; anterior canal 

 short, outer lip sinuous. 



This shell differs from the figures of B. calcarata, composita, and 

 stenoptera of German authors in the length of the wing and want of 

 ribs crossing the keels on the last whorls. It was found in the cast 

 bed of the Grey Chalk, at Lyddenspout, between Folkestone and 

 Dover, and is described from a single specimen. 



Dimorphosoma spathochila, 1 Gardner. Grey Chalk, PL VII. Fig. 10. 



Shell elongated, turreted, whorls with few very prominent oblique 

 ribs, body- whorl with two keels ; wing simple, at first constricted, 

 then widening into a bladebone-shaped expansion ; the channel in 

 the wing is nearly straight, and forms an angle of 70° with the axis 

 of the spire ; the wing was probably twice the length of the speci- 

 men figured, and was pointed as usual in this group. Aperture 

 narrow, anterior canal short, and connected with the wing by an 

 expanded outer lip, with sinuous margin. The form of the canal and 

 the connecting lip is similar to that in D. opeatochila, and is an 

 unusual one in the group. 



Found with the species last described, and described from a single 

 specimen. 



EXPLANATION OF PLATE XII. 



Fig. 1. — Dimorphosoma Jcinclispira, Gardner. Natural size. Neoeomian, Atherfield. 



From the Jermyn Street Museum. 

 Fig. la. — D. Jcinclispira. Enlarged twice. 



Fig. 2. — D. ancylochila, Gardner. From the Jermyn Street Museum, Atherfield. 

 Fig. la. — D. ancylochila. Enlarged twice. 



Fig. 3. — D. pleurospira, Gardner. Neoeomian, Peasemarsh. Mr. Meyer. 

 Fig. 3a. — D. pleurospira. Enlarged twice. 

 Fig. 4. — Another specimen. 



Fig. 5. — D. vecliana, Gardner. Aptien. Shanklin, Isle of "Wight. 

 Fig. 6. — A shell enlarged twice. Shanklin, Isle of Wight. 

 Fig. 7. — A cast of the same, showing length of wing and canal. 

 Fig. 8. — Dimorphosoma sp. ? With expanded wing. From the same locality. 

 Fig. 9. — D. calcarata, Sby. Blackdown beds. From Mr. Meyer's collection. 

 Fig. 9a. — D. calcarata. Enlarged twice. 



Fig. 10. — D. calcarata. Showing aperture with internal thickening. 

 Fig. 11. — D. calcarata. To show length of canal, which is usually broken off. 

 Fig. 12, 12«, 12b. — D. calcarata. To show wing with interrupted growth. 

 Fig. 13. — D. neglecta, Tate. Blackdown bed. Mr. Meyer. 

 Fig. 13a. — D. neglecta. Enlarged twice. 

 Fig. 14. — D. neglecta. An old specimen. 

 Fig. 15. — D. neglecta. Showing aperture. 



Fig. 16. — D. toxochila, Gardner. Gault, Folkestone. Author's cabinet. 

 Fig. 16a. — D. toxochila. Enlarged twice. Author's cabinet. 

 Fig. 17. — D. toxochila. Another specimen. Author's cabinet. 

 Fig. 18. — D. doratocJiila, Gardner. Gault, Folkestone. 

 Fig. 18a.— D. doratochila. Enlarged twice. 

 Fig. 19, 20. — Other specimens of same species. Nat. size. 

 Fig. 21. — D. doratochila. Shows denticulated aperture. 

 Fig. 21a. — Same enlarged. 



Fig. 22. — D. doratochila. Apex very much enlarged. 

 Fig. 23. — D. opeatochila, Gardner. See also Plate V. 

 Fig. 24. — Aporrha'is ? sp. nov. Grey Chalk, Dover. 



1 (nrddr), a blade. 



