14 



TYPE AMMONITES— VI Feb. 



quite different in date from the Kimmeridge Clay Nodule Bed of 

 Oxfordshire. P. lydianites (T.A. DCIV) is from the Lower Portland 

 Pebble Bed, Hartwell, near Aylesbury, Bucks. 



The forms figured by Dr. Neaverson (Amm. Upper Kimm. ; Geol. 

 Dept., University of Liverpool, 1925) as Pallasiceras, from Chapmans 

 Pool are, by the suture-lines which he has given, Lydistratites. Of those 

 for which he has not given suture-lines it is impossible to say whether 

 they are Pallasiceras or Lydistratites. His Pallasiceras ultimuni from 

 Hartwell, near Aylesbury, has neither the suture-Hne of Pallasiceras 

 nor of Lydistratites, and possibly it has no relation to either genus. 

 No evidence of any connection is given. 



Lydistratites, S. Buckman, 1922, Genotype, L. lyditicus, T.A. IV, 

 CCCLHIa. a serpenticone biphcate developed from a virgatite. The 

 inner whorls of the holotype show traces of approximate parvicostation. 

 The suture-line is more longilobate than that of Pallasiceras and Li, 

 L2, increase in length with age ; ES also increases, but not so rapidly. 



Lydistratites lyditicus has been figured in T.A. (CCCLIHa-d) from 

 the Pebble Bed at the base of the Portland-Stone series of Long Crendon, 

 Bucks, from [Upper Lydite Bed of Swindon, Wilts], from Nodule Bed 

 of Chapmans Pool, Isle of Purbeck, Dorset. Forms figured by Dr. 

 Neaverson (Amm. Kimm. 1925), with suture-line, as Pallasiceras from 

 Chapmans Pool belong to Lydistratites, see Pallasiceras (p. 13) . Lydistra- 

 tites biformis and L. cunctator are figured (T.A. DCV, DCVI) from Lydite 

 Pebble Bed of Hartwell, near Aylesbury, Bucks. 



HoLCOSPHiNCTES, Neaverson, (Zones of the Kimmeridgian ; Geol. 

 Mag. Ixi, 1924, p. 149). " Holcosphinctes pallasioides gen. et sp. nov. 

 (= Am. biplex H. B. Woodward, Middle and Upper Oolites : Metn. 

 Geol. Surv., p. 156, fig. 72, 1895), of which specimen No. 30721 Coll. Geol. 

 Surv. is genotype and holotype." 



The genus differs from Lydistratites and Pallasiceras in that its 

 primary ribs are short, and the secondary ribs commence well on the 

 lateral area, while in the other genera the primary ribs extend nearly 

 to the peripheral border before bifurcating. The suture-line also differs 

 from Pallasiceras in being more lobate and from Lydistratites in EL < Li 

 instead of EL > Li. 



H. pallasioides has been figured (T.A. DLXIX) from the Crendon 

 (Hartwell) Clay of Long Crendon, Bucks. Dr. Neaverson (Amm. Kimm., 

 1925) depicts H. pallasioides and H. flexicostatus (PI. in, 5, 6) from 

 Hartwell Clay, of Hartwell, near Aylesbury, Bucks. 



Paravirgatites, S. Buckman, 1922, T.A., IV, CCCVIII, Genotype 

 P. paravirgatus. Somewhat like Pallasiceras in ribbing, only that the 

 furcation-point is much nearer the umbilical edge. The venter is well 

 rounded off, not flattened, as in Pallasiceras. The suture-line is short- 

 lobed, and in this respect agrees with topotypes of Pallasiceras from 

 the Nodule Bed of Cliapmans Pool. 



P. paravirgatus (PI. CCCVIIIa) is from the coarse grit of the 

 Shotover Grit Sands of Shotover, near Oxford ; that of PI. CCCVIIIb 

 is, by matrix, from the Cemetery Beds of Swindon, Wiltshire; P. desider- 

 atus is from Long Crendon, Bucks, among sands (Hudleston label and 

 Collection), that is, from Thame Sands ; P. infrequens (PL DCIII) was 

 obtained in place from the hard layers of sandrock at the top of the 

 Thame Sands of Thame, Oxfordshire. 



