336 THE OCEAN WOULD. 



the heart rejoicing in manhood's strength." In PL. XVIII. some of 

 the principal species are represented, along with some of the more 

 remarkable species of Cytherea. In Fig. 143 we have the elegantly 

 pencilled shell of Cytherea geograpliica, together with the animal in 

 its natural connection. 



The sub-section we shall now treat of is without the pallial line 

 sinuated. The Cyprinidae form the ninth family of onr arrangement 

 of the Conchifera, and contain, Cardia, Cypricardia, Isocardia, Cras- 

 satella, Astarte, Circe, and Cyprina, which amount together to some 

 hundred species. 



The Cycladidae are our tenth family, and include Cyrenoides, Cyrena, 

 Pisidium, and Cyclas. 



The Lucinidae is the eleventh family, containing Galeomma, Lepton, 

 Montacuta, Kelia, Diplodonta, Corbis, and Lucina. 



In the small family of which we have made the Tridacna the repre- 

 sentative, as well as in some preceding families, the mantle of the 

 animal is more or less largely open, but never with such a prolonga- 

 tion as to form tubes. In the Cardiums, now under consideration, as 

 well as Donax, Tellina, and Venus, the respiratory organs are some- 

 what modified, so as to adapt them to the habits of the animal. All 

 these molluscs live buried in the mud or sand, and two great tubes 

 issuing from the interior of their bodies bring the atmospheric air into 

 communication with their respiratory organ namely, the branchial 



The twelfth family, Cardiadae, contains the familiar cockles 

 Cardium which is derived from /capbla, a heart, which they are 

 supposed to resemble in form, are amongst the most widely-distributed 

 of shells. The shell is convex, as we see in C. hians (Fig. 144), 

 somewhat heart-shaped, equivalved, the edges dentate or corrugated, 

 the hinge furnished with four teeth upon each valve. The accessary 

 ornaments vary with the species, some being smooth, as in Cardium 

 Greenlandicum, Chemnitz (Fig. 145) ; others, and by far the greater 

 number, are furnished with regular sides, generally obtuse, sometimes 

 in ridges diverging from the point and armed with straight or curved 

 spines, arranged in the oddest manner, as in Cardium aculeatum 

 (Fig. 146). 



In C. hians (Fig. 144), the mantle has a large opening in front, 

 fringed anteriorly with papillae in the form of tentacula; the in- 



