Modiola (Crenella) nexa. 

 short arcuated group. 



73 



PL 29. Fie. 173. Shell illustrative of the 



Genus 4. LITHODOMUS, Gurnet. 



Animal ; similar to that of Modiola. 



Shell ; cylindrically oblong, equivalve, covered ivith a reddish 

 chestnut epidermis, sometimes incrusted ivith chalk ; extremities 

 rounded ; posterior side very short ; umboes small, incurved ; 

 hinge linear, ivith the ligament marginal. 



The Sea Dates of the Mediterranean seem to have been better known to 

 the epicure than to the naturalist. Long after Cuvier distinguished the 

 Lithodomi as a genus, Lamarck included them with the Modiola, and the 

 animal was not described in detail by either. With the additions made to 

 them by Mr. Cuming, we have a group of some thirty species, presenting 

 a very expressive association of characters. The shell is always of a pecu- 

 liarly oblong-cylindrical or wedge-shaped form, and of a peculiar substance. 

 The animal, unlike the rest of the family, is a borer, and is found imbedded 

 in stone, chalk, coral, and in the valves of Spondylus shells, though often 

 extremely delicate in structure. There is scarcely a species which is not 

 beautifully striated, and there are several curiously sculptured with feathery 

 wrinkles or furrows. Another peculiarity consists in the shell being fre- 

 quently incrusted with a deposit of chalky matter, which is sometimes 

 sculptured, and in some few instances is produced beyond the extremity of 

 the valves. Among the small species a few are bearded with bristles. 



The geographical range of the Lithodomi is wide-spread, but partial. 

 There are more species in the West Indies than in any other locality, but 

 the genus is known to inhabit the Philippine Islands, New Zealand, Chili, 

 Mazatlan, and the Galapagos Islands. The edible Sea Date of the Mediter- 

 ranean, L. lithophagus, was described by the older naturalists as a P/wlas. 

 It is to the boring of this mollusk that the celebrated perforations in the 

 columns of the Temple of Jupiter Serapis are due. 



1. Antillarum, Phil. 



2. appendiculatus, id. 



3. argenteus, Reeve. 



4. attenuates, Desh. 



5. barbatus, Reeve. 

 VOL. II. 



/Species. 



6. bi-excavatus, Reeve. 



7. canaliferus, Hani. 



8. castaneus, Dunk. 



9. caudigeras, Lam. 

 10. cinnamominus, Chemn.lh. Gossei, Reeve. 



L 



11. coarctatus, Dunk. 



12. qorrugatus, Phil. 



13. Gumingianus, Bunk. 



14. divaricatus, Phil. 



