COXCIIOLOOr. 139 



Those shells ahound in caloaroous rocks on the coast, and having; excavated tluir 

 burrows, would seem to become fixtures therein, so tightly do they fit into and fill 

 the cavity -n-hieh contains them. 



Mabtksia, Leach. 



Shell equivalve, the front gape closed by a callous plate. Valves regularly 

 divided in front by a furrow, csteuding from the beaks to the base. Lives in fresh, 

 brackish, or salt water. 



,, FLUMiNALis, W. Blauford. Irrawaddy Delta. 



Siib-famili/ TEEEDINIXJE. 



Teredo, Zinnaus. 



The ' Teredo ' or ship-worm differs from the generality of bivalves by becoming 

 fi.xed at a vciy early period of its existence, after which it constructs a shelly tube 

 in the timber whereon it has fixed. The Teredos are, however, amiable and social 

 creatures, never interfering with one another's paths, though often crowded together 

 as closely as it is possible for them to be packed, whereas some burrowing shells, as 

 Lit/wdomun, cut clean through any opposing substance, even though the same should 

 be the body of an unofi'ending brother bivalve. 



* ,, {Calohiites) tiioeacites, Gould, 

 and several undetermined species. 



Class PTEROPODA. 



Of tlie Pteropods of the Burmese seas we know nothing. These beautiful 

 oceanic creatures are crepuscular in their habits, sinking far from the surface during 

 the day, and rising again towards evening; hence the}- are only to be captured by 

 a net of muslin or bunting suspended during light winds from a .sailing slii]i during 

 the night. Their tiny and exquisitely beautiful shells are ceaselessly 'raining' 

 ■ down into the abj'smal dejjths of the ocean (as the animals die), and are filling up 

 its hollows with an im])alpable mud, somewhat analogous to the English chalk, of 

 which it is no poetic figment to say " The dust we tread upon was once alive." 



Order SCArHOrODA. 



Head rudimentary. Mouth surrounded by filiform tentacles. Eyes none. Heart 

 none. Branchia; none. Sexes distinct. 



Shell tubular, curved, perforate at each end. 



Family DentaliidsB. 



*DENTALirai ooTOGONTJSf, Lam. 



* ,, LOXGiTKOEsuM, Eecve. 



* ,, G/U)us, Mont. 



Identical, _^(^« Hanley, with British examples (sed ?). 



Class GASTEROPODA. 



Locomotion effected by the ventral disk or foot. A distinct head in nearly all, 

 with one or two pair of tentacles. A heart, liver, and convoluted intestine present, 

 and tlie mouth furnished with a radula or ' lingual ribbon,' as it is called, ;u-med 

 with teeth. 



Sub-class OPISTHOBRANCniATA. 



Gills exposed or slightly covered by a fold of the mantle, situated behind the 

 heart, and never lodged in a distinct cervical cavity. Sexes united in the same 

 iiidi\ idual. Larva shell-bearing, and furnished with deciduous cephalic fins (H. and 

 A. Adams). 



