C O N C H O L O G Y. 



fltort, and he balances liimfelf and extends them as he 

 Iwims. The two hinder ones, longer than the others, he 

 plunges in the iea, to ferve as a rudder; and thele up- 

 hold the ikin, or membrane, which he ules for a lail to 

 catch the wind. Thus equipped, he navigates in cala 

 weather; wiien feait'ul of danger, he retires within the 

 (hell, by which action it gains water, and fniks. He of- 

 ten pumps the water out, and alio quits the fliell, which, 

 floating cmptj', is carried by the waves, and either thrown 

 on (lioi e, or dalhed to pieces on the rocks. 



The fi(h can quit the fliell at pleafure, for he appears 

 not to be attached to it by any part of its bod)'. Fre- 

 quently he turns himfelf and Ihcll topfy-turvy, and rifes 

 with his head downwards from tl.e bottom of the fea ; 

 and, when he has gained the furfice of the water, he 

 turns his fliell very nimbly, empties tlie water, extends 

 his arms, and fets fail. They are frequently taken with- 

 out their ihells ; and the fidiermen niuft be extremely ex- 

 pert to catch them in it. This account, however, fetms 

 Ibmewliat doubtful, becaufe we know not of any animals 

 that have proper domicilia, who quit them voluntarily. 

 Fear or necefiity may polTibly caufe this feparation fome- 

 times. Belidcs, as this animal may be fuppofed to frame 

 its own habitation, like others of the teftaceous kind, it 

 ieems necefTary to have ah attachment, however flight, to 

 fome one point, as that fiom which it uniformly extends 

 kfelf for the formation of its fliell ; if this were not the 

 cale, is it poflible to conceive, that a fliell fo delicate, fo 

 regular in every refpeft, could be fabricated ? Knorr en- 

 deavours to account for this phenomenon, by fuppoflng 

 that the tentacula or arms of thefe animals, and even 

 their fibres, art as fuckers, and that they thus keep thera- 

 felves attached to their fliell. For it is well known, that 

 in this manner, if two linooth adhefive bodies touch one 

 another in many places, they make a cohefion nearly as 

 ftrong as though they were united together : and who 

 can decide whether tlie inhabitant of this fliell does not 

 ftick by fibres infinitely fmall in the cavities of the 

 ferratures which are found on the keel ? and whether thefe 

 fibres do not confdt of a vifcous liquor, which prel'ently 

 diflTolves ; and for that reafon cannot fo readily be ob- 

 served ? The uncertainty, however, of the mode of con- 

 taft between this animal and its fliell, h.as rendered the 

 manner in which it conftiufts its abode very queltiona- 

 tle; for there are fome naturalilts who icarcely conceive, 

 by the formation of the fliell, that a cohefion of any part 

 of the animal's body therewith can be at all neceflarj' ; 

 for in that cafe, fay they, it would contradl the growth of 

 that part of the fliell which adheres to the animal: yet they 

 cannot explain how the part which is free from the fliell 

 can increaJe itfelf, though theie are fimilar procefles ob- 

 ferved in nature. As when, for inftance, a filk-worni is 

 changed into the trvf.alis or aurelia, it conftruCls its fliell 

 from its external Jkin ; and taking the form of a butter- 

 fly, it keeps itl'elf during the lail period in this fliell, with- 

 out being attached, and afterwards freely comes out at 

 its own pleafure. Now, might not the paper nautilus 

 conftruft abb a covering round its body from its own 

 vifcons moifture, which, afterwards growing hard, would 

 come off from the minimal entirely, and leave him a free 

 habitation ? This might really be the ca/e, though it is 

 .offered as a mere fuggellion. The animal being now dif- 

 engaged, the fliell becomes thicker by the vifcous matter, 

 which runs through the pores of the animal, or which it 

 receives from the orifice of the new additions or folds, as 

 the fize of the fifli increafes. There is no foundation to 

 fuppofe that the polype, ibmetimes taken in ihis fliell, is 

 its natural inhabitant. And although we all agree that 

 this creature is faftened lefs firmly to its fliell than other 

 tellaceous animals, yet we cannot but fuppofe that it is 

 united, and has coniaft by fome effeLtual means, though 

 4S yet undilcovered, and unafcertained by man. How 

 ell'e are we to explain the increafe of its elevated fides ; 

 the growth of the blunt teeth fymmetrically ranged ; and 

 theorganicalftrui'turedjlcovered by Mr. Hu:tfiant,without 



Vo,i.. V. No. 751.. 



a fuppofition of there being a fyftem of veins or arteries 

 within the fliell, efpecially fince the animal has a form I'o 

 totally different from that of its abode ? 



For a corredl view of this fliell, which is the argonauta 

 argo of Linnasus, fee the Conchology -Plate V. 



AURIS COCHLEAE, or EAR-SKAPED SNAIL- 

 SHELLS. 



The eighth family is formed of the ear fnails, or auris- 

 cochlea, a combination of two names, which exprefles 

 the affinity thele ftiells have to the fea ears, while, at the 

 fame time, they are truly a kind of cochlea or fnails. To 

 this clafs belongs the Venus ear. Their ftiape fo much rc- 

 fembles the fea ears, that molt authors have ranked them 

 in that family, and call them non-perforated fea ears. 

 Lifter and Gualtieri rank them as coUileae, and Linnsus 

 places them in his genus helix. 0a Coita defines the 

 auris -cochleae as follows : fliells (b wide and open as to re- 

 femble fea ears, but are not perforated or fet with a row of 

 holes. They have a broad ledge along one fide, which 

 projedts over the cavity, and turbinates into one (ingle 

 flat fpire, quite even or level with the bottom of the fliell. 

 This fpire is alio very wide ; and extends to near the 

 middle of the bottom or under part : fo that this family 

 abfokitely participates of the charafters and fliapts of 

 the fea ears, and of the fnails, and is, as it were, a com- 

 bination of thole two families, as alio one of the innume- 

 rable inftances of the infenfible progieflions nature takes 

 from one family to another ; which progrelTions baffle hu. 

 man abilities to limit, or the refined definitions of the 

 molt accurate naturalifts. Though there are great num- 

 bers of thefe fliells, yet there are not many diflerent fpe- 

 cies of them. They are figured in the engraving as the 

 next in order to the argonaut, or paper nautilus. 



The CYLINDRI, or OLIVES. 



Thefe fliells are a fpecies of voluta, and conftitute Da 

 Cofta's ninth family. They are of a cylindric form, and 

 pointed at the lower end ; the mouth is long, narrow, and 

 notched on the top; the notch turning backwards, is 

 large and fomewhat awry, like the mouth of a flat fifti; 

 the pillar is faced halfway down, and is greatly wrinkled 

 or plaited ; the turban is generally fliort, very pointed, 

 with the whirls or fpires nearly level, or merely promi- 

 nent one fi'om the other ; and the turban itlelf is divided 

 from the body by only a mere prominent line. 



This family, in moft authors, is clalTed nearly in the 

 fame manner. Lifter calls them, rhombi five ftrombi cy- 

 lindracei. Rumphius forms a genus of them which he 

 calls cylindri. Argenville makes them his eleventh fa- 

 mily, and names them rhombus, cylindrus, or olea. Da- 

 vila places them as two genera of volutes, viz. as the ie- 

 cond genus or cylindrical volutes or rouleaux, and as the 

 third genus or dentated volutes or olives ; and Meulchen, 

 whofe feventeenth genus they are, alio calls them cylin- 

 dri five daCtili. Gualtieri names them cochleae cylindroi- 

 dese, and places them the next genus after the volutes; 

 and Linnseus ranks them in his genus of voluta, by ilie 

 name of cylindroidere. 



This family admits of being divided into two genera, 

 riz. I. Cylindri emarginati, or fuch ivhofe edge is quit* 

 even and fliarp. And, 2. Cylindri marginati, or luch 

 whofe edge is not fliarp and fmooth, but has a very thicjt 

 border, which turns over into a very prominent ledge on 

 the back like the helmets. The fpecies of this family 

 are numerous, and are very beautiful fticlls. Specimens 

 of them are given ill the copper-plate. 



The VOLUTES and CONES. 



The tenth family of this divifion of univalves is the 

 volutes and cones. It is very numerous in its fpecies, 

 and is the family wjiich, for richneis and beauty of co- 

 louring, furpafi'es alraoft all the other univalves, and is 

 reckoned the great ornament or capital obieft of collec- 

 tions. The far greater number of cones always bear 3 



H value; 



