28 MOLLUSCA FROM THE GREAT OOLITE. 



PURPUROIDEA GLABRA. Plate IV, figs. 5, 5, 6, 6. 



P. Testa turbinatd, ovatd ; spird exsertd ; anfradibus^ angulatis, angulis tuber culos 

 10 gerentibus ; anfractu ultimo ventricoso, laevi, basi truncatd; aperturd magnd. 



Shell turbinated, ovate ; spire elevated ; whorls 5 6 angulated ; angles tuberculated ; 

 tubercles 10 in a volution; the last whorl ventricose, smooth, the base truncated; the 

 aperture large. 



In the young state the spire is simply convex, without tubercles, which are only faintly 

 visible upon the last whorl. In every stage of growth the tubercles are less conspicuous 

 than in either of the other two species, and the surface of the last whorl is entirely destitute 

 of ribs and of a second circle of tubercles ; the spire is smaller than in P. nodulata, but 

 more elevated than in P. Moreausia. The length of the aperture is three fifths of that of 

 the entire shell. 



Locality. It accompanies the other congeneric forms in the Minchinhampton Great 

 Oolite, but is very much the most rare of them. The proportion of each species is probably 

 as follows : P. Moreausia, 50 ; P. nodulata, 5 ; P. glabra, 1. 



PURPUROIDEA NODULATA. Plate V, figs. 1, la, 2, 3, 4. 



MUEEX NODULATUS, Young and Bird. Geol. of Yorkshire Coast, p. 245, t. 11, fig. 3. 

 TUBEROSUS, Sow. Min. Con., t. 578, fig. 4 ; but not t. 229, fig. 1, which is a 



Tertiary shell. 

 PURPUKA LAPIEH.REA, Buvignier. Mem. Soc. Philomath. Verdun, 1843, p. 27, 



pi. 6, fig. 21. 



PURPUROIDEA NODULATA, Lycett. Annals of Nat. Hist., 1848, p. 250. 

 MUREX TUBEROSUS, Brown. Illust. Foss. Conch., p. 59, pi. 34, fig. 19. 



P. Testa turbinatd, ovatd; spird escsertd ; anfractibusb 6 angulatis; angulis tuberculos 

 (9 11) plerumque elatiores gerentibus ; anfractu ultimo subventricoso, tuberculis binis 

 cincto, props basin transverse carinato ; tuberculis inferioribus minoribus, approximatis et in 

 costulis lonffitudinalibus obliquis productis : aperturd magnd subquadratd, labro dextro 

 sinuato. 



Shell turbinated, ovate ; spire elevated ; whorls 5 6 angulated ; the angles tubercu- 

 lated; the tubercles usually elevated, 9, 10, or 11 in a volution; the last whorl ventricose, 

 encircled with two rows of tubercles ; those on the second row are much the smaller, and are 

 more closely arranged, and prolonged into longitudinal oblique ribs, which are sometimes 

 nearly obsolete ; below the ribs is a transverse keel, placed near to the base of the shell. 

 The aperture is of moderate size, the outer lip being much sinuated. 



The first two or three whorls are convex, and destitute of tubercles ; the tubercles 

 vary much in size in different specimens when very much elevated they are com- 

 pressed laterally. In the young state, the apex of the spire is more acuminated, the surface 



