MAZATLAN BIVALVES 107 



period of the Coralline Crag, it is natural to suppose that it has 

 now a wide distribution, though its station is such as generally 

 to elude discovery. It would be premature to pronounce 

 absolutely on its specific relations, before the animate have 

 been examined, and other seas more thoroughly searched. The 

 extreme forms are quite sufficiently marked to allow of specific 

 distinction, just as Capt. Brown has described 3 species from 

 the British varieties ; but the known propensities of nestling 

 bivalves, and the presence of intermediate specimens with ever 

 varying characters, do not justify this course. The smallest 

 specimen is '02 across: the largest measures long. '24, lat. *26, 

 alt. ' 15. 



Hob. British seas, Auct. Mediterranean, Philippi. Cana- 

 ries, M* Andrew. Mazatlan ; not uncommon in crevices of 

 shells, generally young ; L'pool fy Havre Coll. [A species 

 probably identical is from Peru ; ,Col. Cuming. The Chironia 

 Laperousii of Desh., from Monterey, Mr. Hartiveg, is quite 

 distinct.] Fossil : British Coralline Crag ; Searles Wood. 



Tablet 485 contains 12 pairs, of various sizes. 486, 10 pairs 

 of valves, very young. 487, 10 do, adolescent. 488, 2 sp. which 

 had lived inside a dead Sphaenia fragilis, which had lodged 

 in the hole of a Lithophagus aristatus, which had bored in 

 Murex regius. 489, 4 sp. in situ, in Spondylus calcifer, Patella 

 Mexicana, and Trivia sanguinea. 



Tablet 490 contains 1 sp. much inflated. 



Tablet 491 contains a pair of valves, with short truncated 

 teeth : [? var.] 492, 2 pairs and a valve, orbicular. 



Tablet 493 contains 3 valves, ligamental pit prominent ; 

 [Pvar.] 



Tablet 494 contains the valve with the honeycomb pattern. 



GENUS LASEA, Leach. 



Lasea, Leach ms.B. M. Cat. Br. Moll. pt. vii. p. 81 : 

 Phil. Hand. Conch, p. 345. Lassea, Brown, III. Conch. Gr~ 

 Br. 1827. Lessea, Moll. 1842 Phil. 1845. 



Bornia sp., Phil. 1836. 



Cycladina, Cantraine, 1836, Bull. Ac. So. Brux. 



Poronia, Recluz, 1843, Rev. Zool. p. 166. 



Kellia pars, Forbes fy Hani. Br. Moll. 1850, vol. ii. p. 85* 



Autonoe, Leach, (a secunda manuj Br. Moll. 289," 



