46 TYPE AMMONITES— III July 



venter. Gloucestershire and Dorset. This genus is distinguished by 

 the pronounced development of smoothness : there are no ventral ridges 

 developed towards end of body-chamber. The direction of growth-lines 

 across venter show that anamorphs and brephomorphs should have 

 forwardly-arched ribs. The genus is also distinguished by the deep 

 funnel-shaped umbilicus. Had the cadicone stage persisted with relative 

 narrowing of umbilicus, a sphaerocone would have been produced : 

 but whorl-reduction and umbilical expansion came on too early. It 

 shows, however, how the sphaerocones of the Tulitidae (Sphceromorphites 

 and the bullatus-like forms) have been produced. 



M. madarus, n. (Ammonites subcontractus, Morris & Lycett, 

 op. cit., p. ii, dimensions ; PI. n, fig. za, pars). Thin test preserved, 

 not abraded ; body-chamber nearly complete. Minchinhampton, Glos ; 

 Great Oolite, a greyish, fawn-coloured, hard, non-oolitic limestone, 

 presumably part of the Weatherstones or of the Basement Bed, or from 

 a local deposit associated with them, but not specially noted ; Geol. Surv. 

 England, ex Lycett, Coll., 25615 ; Genotype and Holotype ; S. 76, 41, 

 82, 30-5 ; 123, 36, 57, 33 ; max. c. 130. 



M. calvus, n. Like M. madarus, but much thinner, because 

 reduction in thickness — incipient serpenticone stage — begins at a much 

 smaller diameter. Test partly preserved, thin, especially on body- 

 chamber. Troll, near Thornford, Dorset ; Fullers' Earth Rock 

 (Thornford Beds — from a hard layer, not unlike the matrix of M. madams) ; 

 S.B., ex Darell, Coll. 1917 ; Holotype ; S. 63, 40, 76, 26 ; 80, 39, 65, 29 ; 

 99, 37, 56, 32 ; max. c. 108. 



M. pravus, n. Like M. calvus, but reduction in thickness of 

 whorl commences at a smaller diameter, and is pronounced enough to 

 produce a contracticone. Umbilical expansion also becomes considerable. 

 Troll, near Thornford, Dorset ; Fullers' Earth Rock, Thornford Beds — 

 a stratum with a slight pinkish tinge, not quite so hard as the matrix of 

 M. calvus ; S.B., ex J.B., Coll. 1921 ; Holotype ; S. 61, 41, 69, 29^5 ; 

 73. 33. 68, 35-5 ; 92, 30, 44, 39 ; max. c. 108. 



Rtjgiferites, g. n. Genotype, R. rugifer, n. Cadiconic passing 

 to incipient serpen ticonic with rounded venter ; costate, (not nodate), 

 primary ribs of low relief, slightly rursicostate on inner margin, then 

 becoming about radial ; secondaries do not pursue course of primary, 

 but start forward at somewhat of an angle, and sweep with a fairly good 

 curve over venter ; some trifurcation of primaries, sometimes by later 

 furcation of second secondary. As umbilicus opens, primaries tend to 

 fail ; secondaries remain, but become distant folds of low relief — somewhat 

 of Morrisiceras-pattem. S.l. simple, but lobes somewhat long ; EL. 

 longer than Li, L2 broad, in two branches, the outer tridactyloid, the 

 inner simple, the incision between not deep, just deeper than between 

 lobules of outer branch. England, Dorset. 



R. rugifer, n. S.B., ex J.B., Coll. 1916, Holotype ; Troll, near 

 Thornford, Dorset ; Fullers' Earth Rock, Thornford Beds, a hard grey 

 limestone ; S. 54, 46, 70, 26 ; 91, 385, 49-5, 35 ; max. c. 100 ; body- 

 chamber about a whorl ; S.B. Coll. 2762, ex F. H. Butler, Paratype ; 

 " Sherborne, Dorset " [Fullers' Earth Rock, Thornford Beds], a hard, 

 grey, crystalline limestone ; S. 29, 35, 61, 33 ; 38, 43, 71, 31-5 ; c. 28 

 primary ribs producing about 68 secondaries ; some irregularity in size 

 of ribs and some suggestion of constrictions. 



PLEUROPHORITES, g. n. (Macrocephaliles, Auctt.). Genotype, 

 P. pleurophorus, n. Sphaeroconic passing to incipient serpenticonic ; 

 costate, primary costse little larger than secondaries — the costaa begin 



