508 HISTORY OF CONCH0L0GY. 



was, what principles were to guide them in framing the va- 

 rious sections, or what the relative bearing of these divisions 

 on one another should he.* The division of shells primarily 

 into Multivalve, Bivalve, and Univalve had perhaps super- 

 seded the Aristotelian, and many new divisions of secondary 

 rate were of course invented, hut they were arbitrary, 

 founded on no common principle, either too lax or too com- 

 plex to be applicable in practice, cumbersome to the memory, 

 and clumsy in writing. To analyse these methods would be 

 wearisome and unprofitable, — they were next to useless 

 when promulgated, and have now no attraction even in the 

 eyes of the pure conchologist. It is when we rise from their 

 examination that we are in the best mood to appreciate the 

 merits of Linnaeus, and feel inclined to nod in complacent 

 assentation to all the paeans which have been so often sung 

 to his praise. 



Linnaeus having, with a tact characteristic of his genius for 

 system, divided invertebrated animals into two great classes — 

 lnsecta and Vermes, — was less happy in his reduction of the 

 latter into their secondary groups or orders. The testaceous 

 Mollusca occupy one order by themselves, in which there are 

 four sections of equal value — the multivalve, bivalve (Con- 

 chae), the univalves with a regular spire (Cochleae), and the 

 univalves without a regular spire, j- In each section there are 

 several genera defined with neat precision, — the characters of 

 the multivalves being derived from the position of the valves, 

 — of the bivalves from the number and structure of the hinge 

 teeth, or, in the absence of these, from a part influencing the 

 opening of the valves, — of the Cochleae from the unilocular 

 or multilocular shell, but in most from the formation of the 

 aperture ; while in the last division the shape of the shell 

 affords the means of discriminating them, excepting in Tere- 

 do which is defined " T. intrusa ligno," in evident contrariety 

 to his principles and his better custom. The naked tribes 

 are placed in the order denominated " Mollusca," where they 

 stand, in " admired disorder," with radiated zoophytes, an- 

 nelidans, parasitical worms, and the Echinodermata, which 

 latter, however, are better in this strange miscellany than 

 they were when they stood either amongst simple or multi- 

 valved shells. 



In estimating the merits of this system it is not fair to 



* From tliis observation D'Argcnville offers no exemption, notwithstand- 

 ing what he has said to the contrary at p. 117, &c, of his Conchyliologie. 



t The expounders of Linnaeus' system do not adopt this last division, — 

 why it is difficult to say. By disregarding it they have injured the natural- 

 ness of the method. 



