210 MYTILIDiE. 



C. decussata, Montagu. 



Minute, obliquely suborbicular ; entire surface radiated with 

 elevated striee. 



Plate XLV. fig. 2. 



XTytilus decussalus, Mont, (not Lamarck), Test. Brit. Suppl. p. 69. — Laskey, 

 Mem. Wern. Soc. vol. i. pi. 8, f. 17. — Turt. Conch. Dic- 

 tion, p. 114. — Fleming, Brit. Anim. p. 411. 



Crenella elliptica, Brown, Conch. Text-book (1833), p. 143, pi. 18, f. 13; 111. 

 Conch. G. B. p. 75, pi. 23, f. 12, 13, 14. 



? Mod 'tola ylandula, Totten, Silliman's Journ. vol. xxvi. p. 3G7, f. 3. — Gould, 

 Invert. Massach. p. 131, f. 87. — Hanl. Recent Shells, 

 vol. i. p. 243. 



Crenella decussata, Macgilliv. Moll. Aberd. p. 229. — Brit. Marine Conch, f. 5. 

 — Alder, Cat. Moll. Northumb. and Durh. p. 82. 



Modiola faba (not Mybilus faba of 0. Fabric), Brit. Marine Conch, p. 248. 



„ cicerctda, Moller. Index Moll. Groenlandice, p. 19. — Hanl. Recent 

 Shells, vol. i. p. 243. 



This pretty little species is very ventricose at the um- 

 bones, whence its convexity regularly and gradually di- 

 minishes in all directions. Its valves are thin and fragile, 

 yet not particularly so for their minute size, and are covered 

 with a rather dull ashy olivaceous or pale olive-coloured 

 epidermis, beneath which the surface appears white. The 

 very many raised and somewhat granulated striae, which 

 radiatingly adorn the entire exterior, are all nearly equally 

 strong, more or less divergent, and very closely disposed, 

 since the interstices, as they widen, become filled up with in- 

 termediate costellar striae ; the granules are much crowded, 

 and very minute. The shape is so obliquely oboval, the 

 beaks are so acute, and project so much beyond the front 

 extremity (which, moreover, is obliquely cut off, as it were, 

 below) that the natural mode of viewing the contour appears 

 to be with the beaks upright and the central strise perpen- 

 dicular ; in which case the former appear exactly in the 



