MAZATLAN BIVALVES 129 
outside.—595, Imp. olivaceus, with bore across the apex.—596, 
do. with 5 Lith. in situu—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 Gastrochena 
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. 
LITHOPHAGUS ARISTATUS, var. GRACILIOR: forma eatlior?, 
“TL. attenuatum” simulante, sed appendicibus curvatis. Long. 
1°15, cujus °22 appendix est, lat. °3, alt. °33. 
Tablet 601 contains 7 sp. of different ages. 
LITHOPHAGUS ARISTATUS, var. TUMIDIOR : formé tumidiori, 
curta, 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. LitHoPpHAGUS CINNAMOMEUS, Chemn. 
Mytilus cinnamomeus, Conch. Cab. vol. viii. pl. 82, f. 731.— 
Eineycl. pl. 221, f. 4.—Desh. Ene. Méth. Vers, pl. 2, p. 566, 
no. 25. 
Modiola cinnamomea, Lam. An. s. Vert. vol. yii. p. 25, no. 18.— 
Hanl. Descr. Cat. p. 238. 
Lithodomus cinnamomeus, B. WM. Cat. Cub. Moll. p. 45, 
no. 539. 
Lithophagus cinnamomeus, Dkr. 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. 
Hab.—Mauritius, Lamarek.— Philippines, Dunker. — Cuba, 
Sagra.— Central America, Dunker.— St. Thomas, Horn- 
beck.—Venezuela, (Porto Cabello,) Tams.—Mazatlan ;_ ex- 
