390 O. C. Crick — Jurassic Cephalopoda — 



tlie superior lateral lobe is decidedly against Grammoceras and in 

 favour of the Sonninince." 



The species of Dorsetensia which seems to come nearest to the 

 Australian fossil is D. Edouardiana (d'Orbigny)/ but the latter can 

 be at once distinguished by the form of its suture-line. 



The present species comes very near Grammoceras toarcense 

 (d'Orbigny) ^ and Grammoceras striatulum (J. de C. Sowerby),^ two 

 forms which have great resemblances, but which are regarded as 

 distinct species by Oppel, Dumortier, and Buckman. The inner 

 whorls of the Australian fossil possess a square peripheral area with 

 a rudimentary sulcus on each side of the carina, and in this respect 

 the specimen more nearly resembles middle-aged examples of 

 Grammoceras toarcense (d'Orbigny) as described by Buckman, Gram. 

 striatulum having an acute peripheral area at all ages. The ribbing, 

 too, is like that of toarcense, but the whorls have no well-defined 

 inner margin, and in this character the specimen resembles Grammo- 

 ceras striatulum (J. de C. Sowerby). The suture-line is more 

 ornamented than in Grammoceras toarcense, and approaches that of 

 Grammoceras Doertense (Denckmann) ; but in the latter species * the 

 first (superior) lateral lobe is not so deep, and the lateral saddle is 

 neither so broad nor so rounded as in the Australian specimen. 



The character of the suture-line distinguishes this present species 

 from " Earpoceras " pseudoradiosum,^ and " Harpoc." subundulatum ,^ 

 Branco, whilst the disposition of the inner part of the suture-line of 

 the Australian specimen separates it at once from such forms as 

 Dumortieria grammoceroides,'' Haug, and D. Levesqiiei^ (d'Orbigny), 

 with which it has certain external resemblances. 



Of the Ammonites which have been recorded from Australia, two 

 only, viz. A. Moorei, Lycett,^ or A. Aalensis, Zieten, var. Moorei, 

 Lycett,^" and A. radians, Schlotheim,'' have any resemblance to the 



1 Pal. Fran^. Terr. Jiir. vol. i. 1842, p. 392, pi. cxxx. fP. 3, 4 (o ?) ; S. S. 

 Buckman, Inf. Ooi. Amni. (Mon. Pal. Soc), pt. vi. 1892, p. 304, pi. xlix. f. 4, and 

 pi. Hi. ff. 8-24. 



2 Pal. FranQ. Terr. Jur. vol. i. 1842, p. 222, pi. Ivii. D'Orbigny wrote the 

 name as Tkouarsensis, which spelling has been adopted by most authors except 

 E. Deslongchamps, who wrote Ammonites toarcensis. Mr. S. S. Buckman [Inf. 

 Ool. Amm. (Mon. Pal. Soc), pt. iv. 1890, p. 172] adopts the spelling toarcensis, 

 ' ' since the name is taken from Thenars, a town in Deux Sevres, of which the 

 correct Latin name is Toarcium." 



^ Min. Conch, vol. v. p. 23, pi. ccccxxi. f. 1. 



* See Denckmann, " Ueber die geognostischen Verhaltnisse Umgegend von 

 Dornten nordlich Goslar," Abhandlungen zur geologischen Specialkarte von Preussen 

 und den Thiiringischen Staaten, vol. viii. pt. 2, 1887, pi. viii. f. 4; pi. x. f . 9 ; 

 and S. S. Buckman, Inf. Ool. Amm. (Mon. Pal. Soc), pt. iv. 1890, pi. xxix. f. 3. 



° W. Branco, " Der untere Dogger Deutsch-Lothringens," Abhandlungen zur 

 geologischen Specialkarte von Elsass-Lothringen, vol. ii. (i.), p. 77, pi. ii. ff. 1-4. 



6 W. Branco, ibid. p. 84, pi. iii. ff. 3, 4, 5 ; pi. iv. f. 1. 



" E. Haug, " Polymorphidse," Neues jahrbuch, 1887, vol. ii. pi. v. f. 5, and 

 woodcut 6c. p. 137 ; and S. S. Buckman, Inf. Ool. Amm. (Mon. Pal. Soc), pt. vi. 

 1892, p. 262, pis. xhd. and xlvii. 



8 D'Orbigny, Pal. Francj. Terr. Jur. vol. i. 1842, p. 230, pi. Ix. 



3 W. B. Clarke, Quart. Journ. Geol. Soc. vol. xxiii. (1867), p. 9. 



10 C. Moore, ibid. vol. xxvi. (1870), pp. 230, 232, pi. xv. f. 1. 



11 W. B. Clarke, ibid. vol. xxiii. (1867), p. 8 ; C. Moore, ibid. vol. xxvi. (1870), 

 pp. 230, 232, pi. XV. f. 2. 



