﻿HUDLESTONIA. 225 



Family — Arietid^e, Hyatt. 

 Genus — Hudlestonia, 1 8. Buchman. 



{Type — Hudlestonia. affinis, Seebach sp.) 



1878. Amaltheus, Neumayr. Unvermittelt auftretende Ceph. ; Jahrbuch k.-k. 



geol. Keichsanstalt, Bd. xxviii, Heft 1, p. 61 

 (group Oxynoti in part). 



1884. OxYNOTtCERAS, Zittel (non Hyatt). Ceph. ; Handbuch der Pal., Bd. i, 



Abth. 2, Lief. 3, p. 450 (in part). 



1889. Pelecoceeas, S. Buchm. (non Hyatt). Cotteswold, &c, Sands; Quart. 



Journ. Geol. Soc, vol. xlv, 

 p. 450, &c. 



1890. — — — This Monograph, antea. 



Adult : Discoidal, compressed, fairly involute. Whorls broad, sloping to 

 form an acute ventral area. Suture-line very simple, lobes short and broad, 

 denticulations very slight. Young : Whorls ornamented with radii some- 

 times bifurcating to form primary and secondary ribs. Ventral area more 

 pronounced, with a small (hollow ?) carina. Sutures with lobes more pronounced. 



Only a few species are included in this genus. They are mostly deficient in 

 ornamentation, and are separable one from another chiefly by the amount of 

 involution or the extent of compression attained. As may be seen from the plate, 

 the material with which I have had to deal has been most unsatisfactory ; and, 

 therefore, it is impossible to be very definite in my remarks. 



The species included in this genus have undergone several changes in regard 

 to their generic classification. Originally placed in the genus Amaltheus — a 

 genus with which they have nothing in common except a sharpened ventral area, 

 a character of no generic value at all — they were removed by Zittel to the genus 

 Oxynoticeras. With this genus they have many points in common ; but the inner 

 whorls of the specimens indicate a certain difference of origin, and I have conse- 

 quently proposed a new generic name. At one time I thought that they might be 

 the species for which Hyatt created the genus Pelecoceras, the description of 

 which seemed to fit them fairly well ; but correspondence with Prof. Hyatt has 

 resulted in my ascertaining that this genus was proposed for something quite 

 different. 2 



1 In compliment to my kind friend Mr. W. H. Hudleston, P.E.S., &c. 



2 Prof. Hyatt writes to me that " Pelecoceras attenuatum, Hyatt, is, if not identical, very 

 similar to the Am. malagma of Dum." (see pp. 142, et seg.). On my pointing out to Prof. Hyatt 



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