2 GO G. W. Bulman — Revised Theory of Glaciation. 



Only a fragment. Bottom Yeovil Sands (I)«sj)ans?<m-becls), Bradford 

 Ablias. 



4. Lytoceras sigaloen,^ n. sp. S. Bnckman (Ammonites jurensis, 

 d'Orbigny (non Zieten), Pal. frang. pi. 100). It has been thought 

 that this is the species Oppel intended to call Amm. dilncidus ; but 

 Oppel's reference is to Qiienstedt's Amm. fimbriatus opalinus, which 

 is that author's name for cornucojnce, d'Orbignj'^ (non Young). 

 Further, Oppel says, "that Amm. cornucopice and Eiidesianus are the 

 nearest allies to dilucidus." It is reasonable to suppose that had he 

 meant to call d'Orbigny's jurensis by the name dilucidus, he would 

 bave said " that Zieten's jurensis was the form nearest to dilucidus." 

 Li/f. sigaloen is like perlavis, but more compressed and more involute. 

 A magnificent specimen, 16 inches (406 mm.) in diameter, is in my 

 collection from Yeovil Sands, Haselbury, Somerset. 



5. Lytoceras Wrighti, S. Buckman. Monogr. page 44, footnote, 

 2, Pal. Soc. 1888. {Lyt. jurense, Wright (noa Zieten), Lias Amm. 

 pi. 79.) Like sigaloen, but very involute. Basin-shaped umbilicus. 

 Oj>iilinum-zone, Dorset, Somerset, Gloucestershire, etc. 



The above species, so far as their suture-lines and inner whorls 

 are known, show clearly enough genetic relationship with Amm. 

 Germanii, d'Orb., torulosus, Zeit., and hircinus (Schloth.), Quenstedt. 

 They lack entirely the extraordinary lengthy lobes — especially the 

 superior lateral — of the Fimbriatns-groni^. 



6. Ammonites linulatus, Quenstedt (Am, Schwab, pi. 48, fig. 2), is 

 another form which may belong to the same group. It differs from 

 Jurensis in having a fan-shaped aperture Avith a high inner margin. 



Whorls depressed. Foreign only. Jurense-zone. 



Three other species have resemblance, but are not exactly allied 

 to Jurensis. 



7. Am. ampins, Oppel. A quick-coiled, very inflated form. Not 

 known in this country. Relationship uncertain. Murcliison(e-zone. 



8. Lytoceras confusum, S. Buckman [jurensis auctorum). A 

 slowly-coiled form with triangular aperture, and marked shoulder. 

 CoHCflWHm-zone, Dorset. The inner whorls and young specimens 

 sometimes show periodic ribs indicating relationship with ophioneum, 

 Benecke, and rasile, Vacek. 



9. Amm. trapeza, Quenstedt. A slowly-coiled, very evolute form, 

 with subtriangular whorls, and more rounded-off shoulder. Very 

 rare, Sherborne-zone with Amm. Jissilobatus (Soioerbyi-zone of 

 German authors). 



V. — The Eevised Astronomical Theory of Glaciation. 

 By G. W. Bulman, M.A., B.Sc. ; 



Corbridge-ou-Tyue. 



IN "The Cause of an Ice Age" Sir R. Ball claims to have 

 removed from the Astronomical Theory of Glaciation the 

 greatest stumbling block in the waj^ of its general acceptance, and 

 to have placed it on a firm and unassailable foundation. And 

 this stumbling block he considers to have been Sir J. Herschel's 

 1 (TiyaXoets, smooth. 



