GRAMMOCERAS DISPANSUM. 211 



Grammoceras DISPANSUM {LijceU). Plate A, figs. 41, 42 (suture-line). 



18G0. Ammonites vaeiaeilis, var. dispansus, Lycett. Proceedings of the 



Cotteswold Club, vol. ii, p. 146. 



1864. — DisPANsus, Seebach. Hanaoverische Jura, pi. viii, fig. 5 a — d. 



1865. — — Lycett. Proceedings of the Cotteswold Club, 



vol. iii, p. 5. 

 1882. Harpoceeas vaeiabile, Wright {uon d'Orbigny). Mouogr. Lias Amm. ; 



Pal. Soc, pi. Ixvii, figs. 3, 4, only. 

 1885. — DisPAKSUM, Haug. Beitrjige Monogr. Harpoceras ; Neues 



Jahrbuch fiir Mineral., &c., Beil.- 

 Band iii, p. 669. 

 1887. Ammonites (Harpoceeas) dispansus, Denckmann, Fauna von Dorn- 



ten ; Abbandl. z. geol. Specialkarte v. 

 Preussen und den Thilringischen Staaten, 

 Band viii, Heft 2, p. 78. 



Discoidal, compressed, hollow-carinate. Whorls broad, flattened, ornamented 

 with ventrally-projected, subsigmoidal radii, which are united into small club- 

 shaped bundles near the inner margin. Ventral area not defined, the two sides 

 of the whorls meeting at a very acute angle, and supporting a large hollow- 

 carina. Inner margin feebly defined, consisting of a slight slope. Inclusion about 

 one-half. Sutures (PI. A, figs. 41, 42) show superior lateral lobe a little longer 

 than siphonal, and not much branched ; inferior lateral about half the size ; 

 auxiliaries generally about three in number. 



Up to 2\ lines diameter the species is smooth, uncarinate, and its whorls have 

 gibbous sides ; at 3^ lines diameter the ribs are present, a small but "distinct 

 carina has appeared, and the whorls are less gibbous. At 6 lines diameter the 

 species has much the appearance of an adult Gramm. toarcense, and the ribs are 

 joined in pairs on the inner area (page 172). 



In a paper read July, 1857, and published in the second volume of the 

 'Proceedings of the Cotteswold Field Club,' bearing date 1860, Dr. Lycett regards 

 Am. dispansus as a variety of ^m. variabilis, and defines it in these words : " The 

 variety dispansus is more compressed, the volutions more enveloped ; both the 

 fasciated tubercles and the ribs are smaller, less prominent, and more numerous, 

 the ribs being much more curved near to the keel." 



The first figure of the species is that given by Seebach, but it cannot be 

 considered characteristic. It apparently represents a specimen without test 

 which does not show the sharp hollow-carina. The figure given by Dr. Wright is 

 the only one which represents the species at all properly. There are two forms of 



