LEPADES. 13 



in the organization of the Lepades, we have felt no little embarrassment 

 in determining the situation they should occupy in the system. Cuvier 

 arranged them as an inferior class of Mollusca ; Lamarck distinguished 

 them as a separate division, equal in rank to those already referred to ; 

 De Blainville divides the Mollusca into Articulata and Inarticulata, re- 

 ferring the Lepades to the former ; and Gray unites them with the 

 Entomostraca, an order of Crustacea. 



The last of these arrangements is certainly deserving of attention, 

 because, upon reference to the descriptive characters of the Lepades, 

 it may be noted, that the most important organs are those by which 

 they are more nearly allied to the Crustacea ; and that as their ana- 

 tomy has become more accurately demonstrated, so their affinity with 

 those animals has been the more fully established ; still, however, we 

 cannot but think, that the production of certain solid testaceous pieces 

 of shell, differing so entirely both in structure and composition from 

 the shell of the Crustacea, fully entitles the Lepades to form a sepa- 

 rate and distinct division, in accordance with the original intention of 

 Lamarck. 



The Lepades may be described as being soft inarticulated animals, 

 entirely destitute of head or eyes ; the body, looking as if reversed, is 

 not articulated, but exhibits some indication of being disposed in trans- 

 verse rings or wrinkles ; it is enveloped in a large integument or mantle, 

 and furnished towards the upper part with numerous articulated tenta- 

 cular cirri, arranged in pairs, and passing through an opening at the 

 top ; the mouth is subinferior, not prominent, and furnished with lateral 

 dentated jaws, as also with a small rudimentary tongue. The nervous 

 system forms a symmetrical series of ganglions. Circulation is per- 

 formed by an indistinct heart communicating with numerous small ves- 

 sels ; and respiration by two or more pectinate branchiae situated at the 

 base of the tentacula, but often concealed. 



All the Lepades are oviparous, and eject their eggs through the orifice 

 at the upper part of the mantle. When the egg is broken, the animal 

 comes forth perfectly developed ; it soon attaches itself to the nearest 

 body, and then begins to secrete certain portions of shelly matter. 



