THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. L 



No. X. — OCTOBER, 1904. 



OE-IG-HnT^^Xj Jk.ieTICLES. 



I. — The Genus Desoeella. 



By Henky Woods, M.A., F.G.S. 



(PLATE XVI.) 



THE genus Desorella ^ was founded by Cotteau in 1855 to 

 include four species from the Corallian named D. icaunensis, 

 D. Orbignyana, D. elata, and D. Drogiaca, and one from the 

 Neocomian — D. incisa. The first and the last of these five species 

 were subsequently shown to belong to the genus Pyrina, the second 

 was placed by Etallon ^ in a new genus, Pseudodesorella, whilst the 

 fourth has been referred to Eyboclypeus. So that of the five species 

 originally regarded as belonging to Desorella, one only, D. elata, is 

 left in that genus. Another species, described in 1862 as Desorella 

 Guerangeri,^ was afterwards shown to be a Pyrina. Cotteau* 

 accepted these modifications, and, in 1873, gave an emended 

 diagnosis of the genus, naming as the type Desorella elata, and 

 describing another species, D. Grasi. M. Jules Lambert is of the 

 opinion that PachycJypeiis semiglobiis (Goldfuss^) should be placed 

 in the genus Desorella. 



All the specimens of Desorella elata and D. Grasi which have yet 

 been described are in the form of internal moulds, consequently the 

 characters of the genus have been hitherto only imperfectly known, 

 so that there was some justification for Duncan's remark, "This is 

 now a very unsatisfactory genus." ^ The description of Desorella 

 given below is based on a specimen with the test preserved which 

 was found in the Corallian of Upware. An examination of this 

 specimen supports the view that Desorella is closely allied to 

 Pyrina, from which it is readily distinguished by its depressed and 

 suborbicular form. Duncan'' placed Desorella in the Nucleolitidas^ 



1 Originally Besoria. 



2 E'tudes paleont. Terr. Jurass. du Haut-Jui-a, pt. ii (1859), p. 16. 



3 Cotteau: Eev. et Mag. de ZooL, ser. ii, vol. xiv (1862), p. 193. 

 * Paleont. FranQ. Ten-. Jur., vol. ix, pp. 333, 384. 



5 Desor: Synopsis E'chin. Foss. (1857), p. 195, pi. xxxvii, figs. 3, 4. Cotteau: 

 Paleont. Francj. Terr. Jur., vol. ix (1873), p. 390, pi. ci. Desor & De Loriol: 

 E'chinol. Helvet. Jurass. (1871), pp. 300, 405, pi. xlvi, fig. 6. 



^ " Ee-\ision of the Echinoidea": Journ. Linn. Soc. Zool., vol. xxiii (1889), 

 p. 179. 



DECADE V. VOL. I. NO. X. 28 



