xx iv INFERIOR OOLITE AMMONITES. 



larger rib, and sometimes there is an intermediate costa which becomes obsolete 

 on the inner part of the lateral area. 



Localities and Strata. — Dorset : Broad "Windsor, probably from the lower beds 

 of the road-cutting at the entrance to the village ; Chideock Quarry, " Wild 

 Bed;" a remarkable specimen showing arrested development in youth, so that 

 the umbilical stout ribs are absent. Somerset : Stoford is the likely locality of a 

 small unlabelled specimen. Foreign : Normandy (Calvados), May-sur-Orne, 

 " Concavum bed " (Dr. L. Brasil). 



Date of Existence. — Murchisonse hemera. 



TOETIEADIATE. 



In the species assigned to the following genera there is a peculiar form of radial 

 line : it recalls with the guide-line the representations of the ivy -twined staff of 

 Dionysus. Hence such radial line may for distinction be termed the caduceiform ; 

 and the genera bearing it may be grouped as tortiradiate. Among the species the 

 caduceiform radial line changes sooner or later to a biarcuate style. 



Generic distinction may depend on the time of this change. Thus : 



1. Changes when lati-gradumbilicate and costate, Depaoceras. 



2. Changes when gradumbilicate and subcostate, Lucy a. 



3. Changes when gradumbilicate and striate, Paineia. 



Remarks. — The tortiradius is an earlier type than the anguliradius of the 

 preceding genera. The evolution may be seen torti-, anguli-, and biarciradius in 

 several species — for instance, Paineia nitens. 



Of the present series Lucya retains the tortiradiate character longest, Depaoceras 

 loses it earliest. 



In the degree of the elaboration of costa? Lucya and Depaoceras are similar, 

 while Paineia is quite distinct. In septation there are several differences. 



XXVII. Genus — Lucya, 1 S. Buchnan. 



(Type : Lucya caduceifera, sp. n.) 



1887. Ludwigia, pars, This Monogr., p. 16. 

 1902. Lucya, Emend. Amm. Nom., p. 4. 



Definition. — Platy-subleptogyral, subangustumbilicate ; subpauci- 

 septate, sublongi-subangustilobate; laterally flexiradiate ; peripherally 

 latanguli radiate, subtalmlate, parvi-nonsepti-carinate. 



Distinction. — From Wiltshireia , by the radial and suture lines ; 

 lhi'e of iMcya" ^ rom Kiliania, by the more flexed radial line and heavier style of 



caduceifera cost ati()11 . 



1 In memory of the late W. C. Lucy, F.G.S., ex-President of the Cotteswold Naturalists' Field 

 Club. 



