L I T 11 D M U S 



Genus LITHODOMUS, Cuvier. 

 Testa transversa, ctfUndraceo-oblonga, cequivalvis, epidermide 

 rufo-castaned induta, calce interdum incrustata ; extre- 

 mitatibus rotundatis ; latere postico hrevissimo ; umbo- 

 nibus parvis, incurvis. Cardo linearis, llgamento mar- 

 gimli. Impressio muscularis eomposita, indislincta. 

 Shell transverse, cylindrieally oblong, equivalve, covered 

 with a reddish-chestnut epidermis, sometimes in- 

 crusted with chalk ; extremities rounded ; posterior 

 side very short ; umbocs small, incurved. Tliiige li- 

 near, with the ligament marginal. Muscular impres- 

 sion compound, indistinct. 

 This very interesting genus, founded by Cuvier, is not 

 alone distinguished from Modiola by the boring habits of 

 its animal. The shell is always of a peculiarly oblong- 

 cylindrical or wedge-shaped form, and of a peculiar sub- 

 stance. It is found imbedded in stone, chalk, coral, and 

 in the valves of Spoiidgliis shells, though often extremely 

 delicate in structure. There is scarcely any species whicli 

 is not beautifully striated, and there are several curiously 

 sculptm-ed with feathery wrinkles or furrows. Another 

 peculiarity consists in the shell being frequently thickly 

 incrusted with a deposit of chalky matter, which is some- 

 times sculptured, and in some few instances produced be- 

 yond the extremity. Among the small species, a few arc 

 bearded with bristles. 



The geographical range of this genus is partial, but 

 widely distributed. There are more species perhaps in 

 the West Indies than in any other locality, but the genus 

 is known to inhabit the Philippine Islands, New Zea- 

 land, Cliili, the Galapagos Islands, and Mazatlan. 



Species 1. (Mus. Cuming.) 



LiTHODOMDS CORRUGATUS. Lithod. testd subcylliidraced, 

 Jlavidd, per totam superfickm striis arcuatis postice di- 

 varicatis corrugatd, extremitate anticd angustd, posticu 

 dilatatd, margine dorsali medio elevato, subangulalo. 



The wrinkled Lithodomus. Shell somewhat cylin- 

 drical, yellowish, wrinkled over the entire surface 

 with posteriorly divaricated arched striffi, anterior ex- 

 tremity narrow, posterior dilated, dorsal margin raised 

 in the middle, slightly angled. 



Modiola cornigata, Philippi, Abbikl. und Besch. Concli. 

 voi.ii. p. 147. pi. 1. f. 1- 



Ila^. Island of St. Vincent, West Indies. 



A yello^visli sliell, rather depressed, with the surface 

 diagonally crossed throughout with waved wrinkles. 



Species 3. (Mus. Cuming.) 



Lithodomus Malayanus. Lithod. testa subtereli, cas- 

 taned, striis perpend icularib us exaratd, area dorsali 

 leevigatii, margine sublrigono-producto, umbonibus in- 

 volutis, parte anticd rn-anifeste angnstiore. 



The Malay Lithodomus. Shell somewhat slender, 

 chestnut, furrowed with perpendicular strise, dorsal 

 area smooth, margin rather angularly produced, 

 umboes involute, anterior portion of the shell mani- 

 festly nan'owed. 



Modiola Malayana, Philippi, Abbild. und Besch. Conch, 

 vol. iii. p. 21. pi. 2. f. 6. 



Hub. Malay. 



A short dark-chcstuut shell, grooved perpendicularly 



over one-half of its surface, the dorsal margin being rather 



angularly produced in the middle. 



Species 3. (Mus. Cuming.) 



LiTHODO.MUS TRUNCATUS. Lithod. testd oblo7igd, ab um- 

 bonibus obtuse angulatd, antice attenuatd, postice tii- 

 midd, angulato-truncatd, medio subcontractd ; nigri- 

 cante-castaned, concentrice rude striata. 



The TRUNCATED Lithodomus. Shell oblong, obtusely 

 angled from the umboes, attenuated anteriorly, pos- 

 teriorly swollen and angularly truncated, a little con- 

 tracted in the middle ; dark chestnut, concentrically 

 rudely striated. 



Gray, Appendix to Dieffenbach's 'New Zealand.' 



Peculiarly distinguished from all other species of the 



genus by its truncated and angularly contracted form. 



Species 4. (Mus. Cuming.) 



Lithodomus gracilis. Lithod. testd elongato-a/lindra- 

 ced, rufo-castaned, in parte anticd striis perpendicula- 

 ribus exaratd, extremitate posticd sensim attenuatd, 

 unticam aquante, margine dorsali convexiusculo, haud 

 ungulato. 



The slender Lithodomus. Shell elongately cylindri- 

 cal, reddish-chestnut, furrowed on the anterior por- 

 tion with perpendicular striae, posterior extremity 



