﻿Yol. 6 1.] GENERA AND SPECIES OF LYTOCEEATIDJ:. 149 



Thysanocekas Oebignit, nom. nov. 



1845. Ammonites cornucopia, d'Orbigny (non Young), ' Pal. Franc, Terr. Jur. : 

 Cephalopodes ' p. 316 & pi. xcix, figs. 1-3 (not fig. 4). 



1867. Thysanoceras cornucopia, Hyatt, Bull. Mus. Comp. Zool. vol. i, p. 96 

 (pars). 



Remarks. — The difference in coiling and the fact that the 

 whorls are depressed, instead of being compressed, separate this 

 species entirely from Young's. Eigs. 1 & 2 are not Oppel's 

 dilucidus (see Al. dilucidum, above, p. 145) : so a new name is 

 required. D'Orbigny's figure is reduced to ^-linear according to 

 the dimensions which he gives : he says that it is ' reduced one- 

 half ('reduite de moitie/ op. cit. p. 318). 



1883. Lytoceras cornucopia, Wright (non Young, nee d'Orb.) ' Monogr. Lias 

 Arnm.' (Pal. Soc.) pt. vi, p. 410 & pi. lxxiii, figs. 1, 2 (3 ?). 



This species differs so entirely in its proportions from Am. cornu- 

 copia, Young, that a new name is necessary. The sculpturing, 

 which is similar to the marks made by pressing a finger-nail into 

 wet clay, suggests the term now proposed. Eroin d'Orbigny's 

 species it differs by less coarse sculpturing, and by a more elevated 

 periphery, making the whorls compressed instead of depressed. 

 In this respect it is nearer to Am. cornucopia, Young, than is 

 d'Orbigny's species. 



Other species are : 



1. Thys. sublineatum (Oppel) = Am. suhlineatus, Oppel.- 



2. Thys. cornucopia (Young) =Am. comucopia,Young, ' Geol. & 



Min. Surv. Yorks. Coast ' (1822) pi. xii, fig. 6 = Am.fim- 

 briatus, Zieten \non Sow.) ' Yerst. Wiirt.' (1830) p. 16 & 

 pi. xii, fig. 1 = Am. Siemensi, Denckmann, 'Fauna des 

 oberen Lias von Dornten ' Abhandl. d. k. Preuss. Geol. 

 Landesanst. vol. viii (1887) p. 156 & pi. i, fig. 5. 



Genus Thysanolytocebas, nov. 

 Genotype, Ammonites Eudesianus, d'Orbigny. 



Definition. — A Lytoceratoid genus, which in suture-line most 

 resembles Lytoceras (fimbriatum-gro\vp), in ornament follows partly 

 Lytoceras, partly Thysanoceras (coimiicopia-series) ; for the main 

 ornament is more of the type of the former, while the crenulate 

 ' flares ' are more of the pattern of the latter, yet in these details 

 the genus agrees with neither. 



Examples. — Thysanolytoceras sp., a heavy stout shell of the 

 Eudesianum-ty^e, JSonninice-Witchellice hemera ; Sherborne 

 (Dorset) ; 3 = ? Am. sidximplus, Quenstedt, ' Ammoniten 

 des Schwabischen Jura ' vol. ii (1886-87) p. 477. 



1 "Ovv%, a nail: ypaTrros, written. 



2 ' Pal. Mitth.' pt, iii. (1862; p. 142 & pi. xliii, figs. 4-6. 



3 There is a giant, of this species in the Cephalopocl-Gallery of the Natural 

 History (British) Museum [No. C 3184], from the Collection of Mr. Darell 

 Stephens, now Mr. R. D. S. Darell, F.G.S. 



