Geological Society. 327 



Oxford University Museum, the attention of the Authoress has heen 

 called to the large amount of prevailing misconception with regard to 

 Sowerby's species Ammonites plicatilis and Am. biplex. The type- 

 specimen of Perisphinctes plicatilis (Sow.) is refigured and described. 

 It is in the form of a cast, but only an indefinite statement exists 

 as to the locality from which it was derived. It appears to be an 

 Upper Corallian form, and is usually taken as the zone-fossil of 

 that horizon. Sowerby's two figures of Perisphinctes bipJex repre- 

 sent different specimens, one of which is dismissed from consideration. 

 The other, probably from a Ivimmeridge-Clay nodule found in the 

 Suffolk Drift, is refigured and described. The Authoress considers 

 that it would be wisest to abandon the name altogether, or at least to 

 restrict it to the abnormal specimen to which it was first attached. 

 The original specimen of Perisphinctes rariocostatus (Buckland) 

 came from the so-called Oxford Clay at Hawnes, 4 miles south of 

 Bedford ; but the Authoress gives evidence in favour of her belief 

 that it was really derived from the Ampthill Clay. Sowerby's 

 Ammonites rotundus is the last species figured, and it is doubtfully 

 identified as a variety of Olcostephamis Pcdlasianvs (d'Orb. ). It was 

 derived from the Kimmeridge Clay of Chippinghurst, 6| miles 

 south of Oxford, and is the zone-fossil of the Upper Kimmeridge 

 Clay. 



2. 'On the Occurrence of Edestus in the Coal-Measures of Britain.' 

 By Edwin Tulley Newton, Esq., E.R.S., V.P.G.S. 



This genus was originally described from the United States, and 

 was afterwards recognized in beds of similar age in Russia and 

 Australia. The genus was afterwards placed with Ilelicoprion 

 and Campyloprion in the family Edestidse. The specimen described 

 in the present paper was obtained by Mr. J. Pringle from one of 

 the marine bands which occurs between the ' Twist Coal ' and the 

 'Gin-Mine Coal,' in the Smallthorn sinking of Messrs. Robert 

 Heath & Son's pits at Nettlebank (Xorth Staffordshire). Several 

 other marine bands, chiefly met with during the sinking of shafts in 

 this coalfield, have been studied by Mr. J. T. Stobbs, who called the 

 attention of the Geological Survey to the exposure from which this 

 specimen was obtained. The specimen is a single segment of a 

 fossil very closely resembling Edestus minor, and consists of an 

 elongated basal portion, bearing at one extremity a smoothed, 

 enamelled, and serrated crown. A description of the fossil shows 

 that it is not to be referred to any existing species, and a new name 

 is given to it. While it seems most in accordance with present 

 knowledge to regard the ' spiral saw ' of Helicoprion as the enrolled, 

 symphysial dentition of an Elasmobranch, possibly allied to the 

 Cestracionts, it does not seem nearly so probable that the forms 

 referred to Edestus are of the same nature. In the opinion of the 

 Author the latter are more likely to be dorsal defences. The paper 

 concludes with a bibliography of the subject. 



