JDr. John Lycett — Note on Purpuroid Shells. 501 



allowance also made for the opposing diflSculties to a correct know- 

 ledge of Purpuroidea which existed thirty or more years ago. 



The front and back views of the shell upon the same Plate, 3, 3cs, 

 are, I am inclined to believe, correctly attributed to Murex ? tuberosus, 

 Sow. The supposed identity, however, rests upon the single specimen 

 now figured, which was acquired by the late Mr. Leckenby only a 

 short time before the transfer of his collection to Cambridge ; the 

 near resemblance which the surface ornaments bear to the Murex 

 nodulatiis of Young and Bird suggests the necessity for caution in 

 deciding upon the separation or identity of those forms as species. 

 Judging from the materials at present possessed by our museums and 

 private collections, I am inclined to believe that the Corallian rocks 

 of Yorkshire possess three species of our genus already figured and 

 described : Firstly, the P. tnberosa, Sow., having a spire apparently 

 as long as the aperture, and a subcylindrical figure of the last volu- 

 tion, exemplified by the very imperfect figure in the Min. Con. tab. 

 578, and by the shell in the Leckenby Collection, figured by Mr. 

 Hudleston in this Magazine, PI. VIII. Figs. 3, 3a. Secondly, by 

 the shorter spired species P. nodidosa, Young and Bird, of which 

 the Whitby Museum has the type, and of wliich a cast may some- 

 times be discovered, named Natica nodidosa. Thirdly, the newly 

 figured three specimens in this Magazine, PL VIII. Figs. 1, 2, 4, 

 a more ventricose species than either of the former, the spire more 

 produced than in P. nodulata, and its surface more elaborately 

 ornamented than either of the other species. The Jurassic Pur- 

 puroidea are limited to limestone formations. Its lowest known 

 position is the Great Oolite of England and of France, we next 

 discover it in the Corallian rocks of England and France, it has 

 also lately been found in limestone of the Portland formation. The 

 species were gregarious and appear to have occupied very limited 

 areas both in their horizontal and vertical range. With much regret 

 I find that at the quarry on Minchinhampton Common, which has 

 been the most pi'oductive site for Purpuroidea in England, the genus 

 is now exceedingly rare and a good specimen of any of its species 

 has become a thing of the past genei-ation. In the Corallian rocks 

 a few miles to the southward of Malton, Purpuroidea has always 

 been difficult to obtain excepting in the condition of internal moulds 

 which retain no portion of the exterior surface. 



After examining the figures of Purpuroidea already published, I 

 would warn authors and artists to be more careful of the position of 

 the specimen when it is intended to figure the aperture. The original 

 woodcut (right-hand figure) published by me in 1848, although a 

 somewhat rude engraving, exemplifies the figure of the aperture 

 fully and accurately ; it directly faces the spectator, and proves that 

 the specimen was entirely without the groove of Purpura. The 

 figure of the aperture of Purpuroidea tnberosa in Geol. Magazine, 

 PI. VIII. Fig. 36, is equally satisfactory, but the aperture of the 

 specimen. Fig. 2, upon the same Plate, has been so placed by the 

 artist as to make the rounded coluniellar lip face the spectator, and 

 conceals the more important posteal extremity of the aperture. 



