MAZATLAN BIVALVES 129 



outside. 595, Imp. olivaceus, with bore across the apex. 596, 

 do. with 5 Lith. in situ. 597, do. with upper part broken 

 across, shewing an inner partition made by the animal to 

 avoid the attacks of 2 Lithophagi ; also a young Gastrochsena 

 in situ. 



Tablet 598 contains extremities of shelly tubes. 599, a large 

 number of posterior extremities, to illustrate the variations of 

 form. 600, fragments to shew the different layers, viz. inter- 

 nal shelly layer, medial epidermis, and external coating. 



LITHOPHAGTJS AEiSTATUS, var. GEACiLiOE : forma exilwrij 

 "L. attenuatum" simulante, sed appendicibus ciirvatis. Long. 

 1*15, cnjus '22 appendix est, lat. '3, alt. '33. 

 Tablet 601 contains 7 sp. of different ages. 



LITHOPHAGTJS AEISTATUS, var. TUMIDIOE : forma tumidiori, 

 curtd, ad L. cinnamomeum prope accedente. Long. 1*54, cujus 

 '35 appendix est, lat. '53, alt. '58. 



Tablet 602 contains 3 pairs and 1 valve, very young. 603, 

 3 sp. young and old. The extreme form of this ? variety was 

 naturally regarded by Dr. Dunker as a distinct species. 



177. LlTHOPHAGTJS CINNAMOMEUS, CJiemn. 



Mytilus cinnamomeus, Conch. Cab. vol. viii. pi. 82, f. 731. 



Encycl. pi. 221, f. &DesJi. Enc. Meth. Vers, pi. 2, p. 566, 



no. 25. 

 Modiola cinnamomea, Lam^. An. s. Vert. vol. vii. p. 25, no. 18. 



Hani. Descr. Cat. p. 238. 

 Lithodomus cinnamomeus, ~B. M. Cat. Cub. Moll. p. 45, 



no. 539. 

 Lithophagus cinnamomeus, DTcr. in lit. 



One perfect valve only was found that could be certainly 

 identified with this species. So weak however was the shelly 

 matter, that on being placed in hot water the cuticle ran into 

 shreds, breaking it to pieces. According to Dunker, the 

 species is of wide distribution, and variable in colour, being 

 brown, chesnut, or cinnamon. This specimen was blackish 

 brown, about an inch long. 

 Hob. Mauritius, Lamarck. Philippines, Dunker. Cuba, 



Sagra. Central America, Dunker. St. Thomas, Horn- 



beck Venezuela, (Porto Cabello,) Tarns. Mazatlan; ex- 



