﻿Vol. 6l.] GENERA AND SPECIES OF LTTOCERATID^. 147 



umbilicus. Inner whorls subcostate, showing the torulosum-sb&ge ; 

 outer whorl smooth, stoutly oval. Inclusion about two-thirds. 

 Umbilicus gradate. 



Distinction. — From P. jurense, a smaller umbilicus, broader 

 whorls, greater inclusion. 



Remarks. — The inner whorl, showing the torulosum-sb&ge, is 

 a most interesting fact in the ontogeny, important for indicating 

 genetic affinity. Such an inner whorl is the morphic representa- 

 tion of P. torulosum. 



Locality and Horizon. — Spratton Ironstone Workings, Brix- 

 worth, near Northampton, in the Northampton Sands. 



Date. — Hemera soissi, presumably; see under Alocolytoceras 

 tamiatum (p. 146). 



Pachylttocera-s phylloceratoides, sp. nov. (PI. XV, figs. 1-2 & 

 PI. XVI, fig. 3.) 



Description. — A Lytoceratoid with a phylloceratan aspect; 

 outer whorl stoutly oval, smooth ; umbilicus quite small, umbilical 

 border fairly steep. 



Distinction. — The parvumbilicus, and the phylloceratan aspect 

 of the fossil. 



R e m a r k s. — In the ' Geology of the Country around Cheltenham ' 

 (Mem. G-eol. Surv. 1857), Prof. Hull notices (p. 30) ' a large 

 ammonite 1 ft. 8 in. in diameter,' which, he says, 'strongly resembles 

 A. heterophyllus,' in Sands [scissum-be&s] at Clapton, near Sher- 

 borne (Gloucestershire). I suggest that it is a parvumbilicate 

 Lytoceratoid closely allied to, or the same species as, the one 

 now under consideration. I do so, because some 20 years ago 

 I saw in the possession of the late Dr. Moore, at Bourton-on-the 

 Water, several giant parvumbilicate Lytoceratoids which had been 

 obtained, during the making of the Banbury & Cheltenham Eailway, 

 from the first cutting on the west, presumably from the Sands. 

 That they were Lytoceratoids with phylloceratan aspect attracted 

 my attention at the time. 



Prom Dorset I have long had a similar large parvumbilicate 

 form ; but I fancy that it is not the same species as Mr. Thompson's. 

 I cannot examine it now. 



Locality and Horizon. — Spratton Ironstone Workings, Brix- 

 worth, near Northampton, in the Northampton Sands. 



Date. — Hemera scissi, presumably. See note to Al. tceniatum. 



II. Other Groups op Jurassic Lytoceraticze. 



In connection with the Lytoceratidae which have been reviewed, 

 it seems desirable to note certain new or incompletely-known 

 genera of this family. It is important for all systematic work to 

 give to each genetic series (or Eormenreihe) its own generic 

 name. For museum-work, for cataloguing, for classification, and for 

 ready identification, the more this system is tried the better does it 



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