figured in Phillips's 'Geology of Yorkshire.'' 481 



The same author founded the genus Cirrus in 1816*, and 

 described it as a spiral conical univalve, without a columella, 

 with the volutions united and funnel-shaped beneath ; type 

 C. acutus, Sow. 



In 1837 Dr. Bronnf established the genus Schizostoma for 

 certain of Sowerby's Euomphali, but with the mouth, as he 

 supposed, sinuated and furnished with a band, as in Pleuro- 

 tomaria and Pleurotoma : type Euomphalus catillus, Sow. 



Prof. L. G. de Koninck J and Prof. F. M'Coy§, writing 

 almost simultaneously, united the genera Euomphalus and 

 Cirrus of Sowerby in one genus, under the name Euom- 

 phalus. The latter of these authors did so " knowing of no 

 character by which to distinguish them ; at the same time 

 I am perfectly aware that Euomphalus, as it now stands, 

 requires revision." Prof, de Koninck, on the other hand, 

 went a step further than M'Coy, and referred the united Euom- 

 phalus and Cirrus to Straparollus, Montf. ; however, to show 

 the widely different outward form represented by such shells 

 as E. pentangulatus, Sow., and C. acutus, Sow., or S. Dionysii, 

 De Montf., he subdivided the combined genus into Euomphali 

 schizostomatoidei and E. cirroidei. 



In 1850 D'Orbigny|| united the three genera, adopting for 

 the combination the name first given by Denis de Montfort, 

 Straparollus. 



The next important contribution to this subject is that by 

 Prof. M'Coy, who, in the second fasciculus of his ' British 

 Paleozoic Fossils ' % restricted the name Euomphalus to those 

 forms with an entire peritreme, and often thickened, nearly 

 entire circular lip, not indented by the preceding whorl : types 

 E. rugosus, Sow., and E. discors, Sow. On the other hand, 

 Cirrus is abandoned, and the name Straparollus used for both 

 those cirroid and planorbicular shells in which the mouth is 

 indented by the preceding whorl. 



The last opinion I think necessary to refer to in this 

 matter is that of Messrs. Meek and Worthen**. These re- 

 markably astute palaeontologists point out that there is a 

 discrepancy between the figures of Straparollus Dionysii, given 

 by De Montfort and De Koninck, in the form of the mouth. 

 On the general question they remark: — "We are aware Prof. 

 M'Coy and some others regard Euomphalus, as typified by 

 E. pentangulatus, as an exact synonym of Straparollus, and 



* Min. Conch, ii. p. 93. f Lethaea Geogn. i. p. 95. 



X Descr. Anim. Foss. p. 418. 



§ Synop. Carb. Limest. Foss. 1844, p. 34. 



|| Prodr. de Pal. i. p. 6. % P. 297. 



** Illinois Survey Report, 1866, ii. p. 158. 



