122 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



tab. 172, of •wljich numerous specimens are now in the British Museum, obtained from a similar geological 

 position in Somersetshire ; in some of these the last volution quite conceals all the others, leaving only a 

 small umbilical orifice ; the absence of costse upon the inner portion of the last volution distinguishes it 

 from A. maci'ocephalus. Dr. Oppel (' Juraformation,' p. 478) proposes for it the new title of A. Morrisii, 

 which, in accordance with the above views, must remain as a synonym of A. viator. 



Acteonina? parvula, Part I, p. 104, alter the generic title to Ceritella. 



Part II, Tab. 5, figs. 18 a, 19 a. Both these figures represent the young condition of Trigonia 

 Goldfussii. 



Trochus pileolus. Part I, p. 66, Tab. 10, fig. 5. Additional specimens have proved that the smooth- 

 ness of the surface is accidental ; traces of encircling striations are sometimes visible ; the shell then 

 becomes identical with Turbo obtusus, Sow., of which Trochus Bixa, D'Orb., is also a synonym. 



Nerita hemispherica, Roem., Tab XI, figs. 14, 16; Nerita minuta, Sow., Tab. XI, fig. 19. A com- 

 parison of very ample materials, including all the connecting forms, leaves no choice but to regard iV. 

 hemispherica as the adult shell of N. minuta. The preservation of the epidermal pattern of coloration has 

 materially tended to this result; the older shells, as in fig. 14, with their strong, rugose plications, thickened 

 columellar lip, and entire absence of the epidermal coat, appear at first sight sufiiciently distinct, but from 

 these we pass to specimens of less advanced growth, as in fig. 16, without plications, but still possessing 

 the callosity upon the inner lip ; some in this state, however, retain portions of the external tegument, in 

 which may be traced remains of the two broad bands of white between the three of dark-coloured pigment, 

 the latter consisting of transverse, wrinkled lines. From these to the smallest forms the transition is easy ; 

 the latter are most commonly more ovate, but this is by no means an invariable feature, nor are the adult 

 shells very constant in the degree in which the spire is produced. The minute forms, which usually retain 

 the epidermal coat, are smooth and shining ; with advance of growth the shell exhibits continual and 

 considerable increase of thickness. The two extremes of aspect are fairly represented in figs. 14 and 19. 

 Nerita minuta is so inappropriate a name for the adult shell, that it seems desirable to adopt Nerita 

 hemispherica, although the former has priority. 



Fusus ? subnodiilosus. Part I, Tab. V, fig. 9, p. 23, alter the generic title to Brachytrema. 



Phasianella conica, Part I, Tab. XI, fig. 30, p. 74 ; Phasianella acutiuscula. Tab. XI, fig. 28, and 

 Tab. IX, fig. 2. An examination of numerous additional specimens has led to the conclusion that these 

 forms should be regarded as only varieties of one species . for although some examples are even more 

 lengthened than the figures of P. acutiuscula, others connect the typical specimens of each variety in a 

 very perfect manner. 



Genus Brachytrema, Part I, p. 24. Further information has shown that the generic description before 

 given should be slightly modified ; the outer lip was stated to be thin, which is correct as far as regards the 

 greater number of specimens ; but some species, as B. varicosa and B. pygmea, acquired at certain an-ests 

 of growth thickened outer lips or varices, as in Triton ; from the latter genus they are distinguished by the 

 shorter trochiform spire and absence of denticulations upon the borders of the aperture. 



Turbo? pygmeus. Tab. IX, Part I, figs. 29, 29 a, alter the title to Brachytrema pygmea. The doubt 

 as to the genus expressed in Part I, p. 60, has been justified in an example with the aperture perfect, figured 

 by M. Piette, 'Bull, de la Soc. Geol. de France,' 2 ser., pi. xv, fig. 21, under the name of Brachytrema 

 brevis ; the base is strongly striated, and the aperture much contracted. 



Ataria Iwvigata, p. 17, Tab. Ill, figs. 3, 3 a,- Tab. XLI, fig. 13, alter the title to Alaria Myurus, 

 Desl., sp. It was stated at p. 17 " that in everything excepting its smooth surface this shell agrees with the 

 Ilostellaria Myurus of Deslongchanips." A specimen recently obtained exhibits some encircling striations 

 upon the upper portions of the two larger volutions ; the sole distinction, therefore, that separated it from 



