78 DH. L. F. SPATH ON THE AMMONITES [vol. lxxix, 



■of Quenstedt, but is immature) and with a compressed variety of 

 the same species. The numerous young Arietites that occur with 

 these forms develop carina and costse at a very early stage. 



In the lenticles 9 feet below the birch i-nod\i\a,Y, and in the 

 birch i-tabula.Y, the Gymbites are associated with young Micro- 

 •deroceras that remain smooth or striate to a considerable diameter, 

 and can be distinguished from Gymbites chiefly by the complex 

 suture-line, the regular coiling, and the striation when the test is 

 preserved. On the other hand, the birch i-t&bvl&Y contains a form 

 comparable to Gymbites (?) semicostulatus Eeynes (non Warmer) 

 .sp., 1 distinguished from the young of Xipheroceras by its greater 

 thickness and comparative smoothness. It may be noted that a 

 small malformed example of a M. birchi from the b irchi- nodular 

 has acquired, after an injury, the outer whorl of a Gymbites 

 Icevigatus, though the mouth-border has a raised lip all round, 

 not a prominent ventral lappet. 



From the evidence of Dr. Lang's collection, Gymbites Icevigatus 

 would appear to be confined to the beds 74d-76; but there is a 

 loose block in my collection that contains the tj^pically excentrum- 

 bilicate Gymbites Icevigatus, in association with X.ipheroceras of a 

 ■late type ; the block probably came from a bed not yet located 

 higher than the foVc/u-tabular. The Gymbites (?) found ' in place' 

 above the birch ^-tabular are small globose forms, that occur also 

 with the Marston Magna Xipheroceras planicosta (typus) ; in the 

 Asteroceras-smithi Bed at Lyme, of the same age as the Marston 

 Marble ; and in the (87) Brachiopod Limestone (No. 1098, Coll. 

 W. D. Lang), but these may be young Asteroceras. At least, the 

 examples that I have dissected are comparable to the young of 

 Asteroceras obtusum ; whereas the development of Gymbites loevi- 

 yatus resembles that of (for instance) Arnioceras nigrum. None 

 of these later forms has a constricted mouth-border or scaphitoid 

 body-chamber, and it may be noted that the forms from Lias /3 

 and S, included in Gymbites by Pompeckj, namely Quenstedt's 3 

 -fig. 46 of pi. xxii, and fig. 38 of pi. xlii, also probably have nothing 

 to do with the Icevigatus group to which Gymbites is here restricted. 

 Mr. Linsdall Richardson's 3 ' Gymbites globosus ' and ' G. cf. 

 personatus (Simpson) ' are ecmally doubtful. 



(G) Genus Sulciferites Spath. 



The family Schlotheirnidse, derived from Psiloceratidse by way 

 of Wcehneroceras, is represented in the material here described by 

 species of Sulciferites, to which genus were referred 4, members of 

 the group of Schlotheimia sulcifera S. Buckman = ^4. sulcatus 

 J. Buckman, non Simpson, the genotype being that species to 



1 ' Monographic des Ammonites ' 1879, pi. xxxi, figs. 27-29. 



2 ' Ammoniten des Schwabischen Jura' 1883-85. 



:i In S. S. Buckman, ' Jurassic Chronology I : Lias. — Suppl. I ' Q. J. G. S. 

 vol. lxxvi (1920) p. 81. 



4 Abs. Proc. Geol. Soc. No. 1079, January 13th, 1922, p. 30. 



