i 5 o MIDDLE ALBIAN STRATIGRAPHY 



When found in condensed phosphatic nodule beds, this species shows a bewildering 

 series of morphological transitions to other coarsely ornamented species of Hoplites. 

 Most of these transitions are more apparent than real, in that coarse members of a 

 number of indirectly related offshoots which developed at slightly different times 

 have been collected together en melee in the same bed. To Spath it appeared that 

 this species belonged to Parona & Bonarelli's Hoplites rudis but was not typical of it 

 (1925a ; 108). H. (H.) rudis does occur in England in the upper dentatus-spathi 

 nodule bed in the northern Weald, however, in the writer's opinion it represents a 

 coarse end member of a different development of Hoplites {H.). 



Horizon & localities. The species occurs throughout the spathi Subzone and is 

 ubiquitous in the Anglo-Paris basin. 



Genus ANAHOPLITES Hyatt 1900 



Anahoplites osmingtonensis sp. nov. 



(PI. 1, figs, ia, b) 



1925a Anahoplites mimeticus Spath (pars) ; Spath : 142. 



1927 Anahoplites mimeticus Spath (pars) ; Spath : 188, pi. 17, figs. 8a, b. 



Derivation of name. From Osmington, Dorset, the type locality. 



Diagnosis. Anahoplites of the intermedins group : discoidal, compressed, evolute, 

 with excentric umbilicus. Umbilical wall steep in early whorls becoming rounded in 

 outer whorl. Umbilical margin marked by faint comma-shaped bullae giving rise to 

 faint striate ribs on gently curving whorl flank, terminating on ventro-lateral shoulders 

 at faint clavi absent on body chamber. Venter subtabulate slightly sulcate. 

 Suture line like A . planus, but symmetrical across venter and highly interlocked. 



Type material. Holotype BMNH., C 68385 (T. F. Grimsdale Coll.). Uppermost 

 spathi Subzone between Osmington Mills and Black Head, Dorset. Paratypes 

 BMNH., C 26595 same collection, horizon, and locality as Holotype. BMNH., 

 37604 (Astier Coll.) condensed Middle Albian phosphatic bed, Escragnolles, Alpes 

 Maritimes, France. 



•33 (Holotype is slightly crushed) 

 •30 



Remarks. This species differs from Anahoplites planus (Mantell) in its marked 

 excentric umbilicus, slightly sulcate venter which becomes broadly rounded on the 

 body chamber, and the symmetrical arrangement of the suture line each side of the 

 venter. The elements of the suture line are closely interlocked resembling specimens 

 of A. planus from the cristatum Subzone. It is, however, probably not directly 

 related to A. planus, an early mutation of which occurs in the same bed (e.g. Spath 

 1927 ; 188, pi. 18, figs. 7a, b), but is very near the stem from which A. grimsdalei, 

 A . evolutus, A . intermedins, A . mantelli, A . praecox, and A . alternatus sprang. 



Dimensions. 









C 68385 



[107] 



•39 



•25 



37604 



107 



•40 



•28 



