A manual of the Mollusca, or, A rudimentary treatise of recent and fossil shells . ncentric, in palndomus lamella)-, in valvata spiral; in solanum and ceri-thiHm,\i is multispiral ox paueispiral. Some of the gasteropoda can suspend themselves by glutinous thieads. GASTEROPODA. 103 like litiopa and rissoa parva, which, anchor themselvesto sea-weeds (Gray), and cerithldea (fi^. 68), whichfi-equeutly leaves its proper element, and is foundhanging in the air (Adams). A West India land-snail { suspensitm) also suspends itseK (Guild-ing). The origin of these threads has not been ex-plained
A manual of the Mollusca, or, A rudimentary treatise of recent and fossil shells . ncentric, in palndomus lamella)-, in valvata spiral; in solanum and ceri-thiHm,\i is multispiral ox paueispiral. Some of the gasteropoda can suspend themselves by glutinous thieads. GASTEROPODA. 103 like litiopa and rissoa parva, which, anchor themselvesto sea-weeds (Gray), and cerithldea (fi^. 68), whichfi-equeutly leaves its proper element, and is foundhanging in the air (Adams). A West India land-snail { suspensitm) also suspends itseK (Guild-ing). The origin of these threads has not been ex-plained ; but some of the limaces lower themselves tothe giouud by a thread which is not secreted by anyparticular gland, but derived from the exudation overthe general surface of the body (Lister; DOrbigny). The division of this extensive class into orders andfamilies, has engaged the attention of many natm-alists,and a variety of methods have been proposed. Cu-viers classification was the first that possessed muchmerit, and several of his orders have since been unitedw^th Fig. System of Cuvier. System now adopted. Class. Gasteroboda. Order 1. Pectinibranchiata ) 2. Scutibranchiata >- Ord. Prosohranchiata, M. Edw. 3. Cyclobrauchiata \ 4. Tubulibranchiata ) 5. Pidmonata Ord. Pulmonifera. 6. Tectibranchiata •) 7. Infcrobranchiata f. Ord. OpistJiohranchiata, M. Edw 8. Nudibranchiata 3 Class. Heteropoda. Ord. Nudeobranchiata. El. ORDER I. well developed, and protected by a shell, into which the wholeanimal can usually retire. Mantle forming a vaulted chamber over the backof the head, in which are placed the excretory orifices, and in which thebranchiae are almost always lodged. BranchioB pectinated, or plume-like,situated {proson) in advance of the hcait. Sexes distinct. (M. Edwards.) SECTION A. SiPHONOSToMATA. Carnivorous Gastcropods. Shell spiral, usually imperforate; apertm-e notched or produced into acanal in front. Operculum horny, lamellar.
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmollusks, bookyear185
