SUPPLEMENT.— DELTOT DOC ERAS. cxvii 



Localities and Strata. — Dorset: Bradford Abbas, Fossil Bed, presumably 

 upper part. 



Date of Existence. — Biscitse, hemera, presumably. 



Deltiradiate. 

 XL VIII. Genus — DELTOIDOCERAS, 1 8. Buck man. 

 (Type: Deltoidoceras astrictwm, sp. n.) 

 1902. Deltoidoceras, Emend. Amm. Nom., p. 3. 



Definition. — Platysubleptogyral, 2 augustimibilicate ; sublongi-subangustilobate ; 

 laterally subflexiradiate ; peripherally subacutanguliradiate, subtabulate, subalti- 

 carinate. (Radial line, fig. 79, p. clxv.) 



Distinction. — From Depaoceras, radial line ; relatively smaller umbilication; more 

 definite tabulation and carination of periphery. 



Remarks. — The similarity of this genus to Depaoceras is suggestive of a common 

 descent from a not very remote ancestor, one akin to Lucya caduceifera. But in 

 this genus the carination and tabulation of the periphery, and the rostration have 

 been carried to a further degree of development. 



1. Dkltoidocebas idoneum, 8. Buchmau. Suppl., Fig. 80 in text. 



Fig. 80. — Deltoidoceras idoneum. 



1 l€\-oei8i)s, delta-shaped. The cross section is deltoid in shape, and the radial line makes w ith 

 the guide line a somewhat deltoid figure. 



2 Medianly subleptogyral, but whorl triangulate. 



