130 MOLLUSCA FROM THE CRAG. 



This is a very abundant shell in the Coralline Crag. Some specimens are strongly 

 marked by the remains of colour, which cross the lines of growth at a considerable 

 angle, others resemble one of M. Philippi's varieties, " maculis longitudinalibus magis 

 minusve confluentibus." The lines of growth are very distinct, and slightly elevated 

 upon the striae, and also between them ; and the number of transverse ridges vary 

 from six to ten. The umbilicus is generally covered, but sometimes it is open. A 

 recent specimen from the Mgean Sea, obligingly sent to me for comparison by 

 Professor E. Forbes, appears to correspond in all essential characters with my fossils, 

 excepting that it is larger ; and the Crag shells are rather more imbricated than the 

 recent shell, which might naturally be expected from the loss of the epidermis. The 

 shell is beautifully nacreous beneath its outer covering. 



12. Trochus Kicksti. Npt. Tab. XIV, fig. 5, a—d. 



Teochus Kicksii. Nyst. Coq. foss. de Belg. p. 381, pi. 38, fig. 2, 1844. 

 - RoBiNsii. - - - p. 382, pi. 38, fig. 3. 



Tr. Testa convexo-conicd, obtusiusculd ; anfradibus 5 — 6, conveximculis, transversim 

 tenuissime striatis ; striis impressis ; columelld obliqud obsolete unidenfatd. 



Shell convex or obtusely conical, thick, and strong ; volutions 5—6, slightly convex, 

 transversely striated, with five impressed striae ; aperture subrhomboidal ; columella 

 obUque, obsoletely toothed. 



Awis, \ of an inch. 



Locality. Cor. Crag, Sutton. 

 Red Crag, Sutton. 



A very abundant shell in the Coralline Crag. The characters wliich most dis- 

 tinguish this shell are the impressed striae and rather smooth exterior ; it differs but 

 in a slight degree from T. Adansoni, and is probably a variety of that species. On the 

 young shell more especially the striae are but few and deeply impressed. The form of 

 the shell, and its slightly convex and overhanging volution, resembles the figure by 

 M. Nyst ; but his description, "undique laevigata," does not fully accord with our shell, 

 as even in my most worn and altered specimens traces of striae may be detected. 



13. Trochus tumidus. Mont. Tab. XIV, fig. 2, a — b. 



Trochus tumidus. Mont. Test. Brit. p. 280, t. 10, fig. 4, 1803. 



GiBBULA TUMIDA. Leach. MS. 1819. 



Tkochus nitens. Woodward. Geol. of Norf. t. 3, fig. 10, 1833. 



— LiTTORALis. Brown. Conch. lUust. of Brit. pi. 45, fig. 1, 4, 1827_ 



— tumidus. S. Wood. Catalogue 1842. 



— — Morris. Catal. of Brit. Foss. p. 165, 1843. 



Tr. Testd convexo-conicd, obtusiusculd, crassd; anfractibu^ tumidis, convexiusculis ; 

 suturis profundis ; superne subangulatis, transversim tenuissime striatis ; ad basim obtuse 

 angulatis ; aperturd subquadratd ; umbilico mediocri, scepe clauso. 



Shell obtusely or convexo-conical, strong, and variable ; whorls tumid, slightly 



