104 LECTURES ON MOLLTJSCA. 



bend. Chamostrea is shaped like Chama, attached on the anterior 

 side, without sinus. They are all peculiar to the Australian region. 



Family PANDORID.E. 



The Pandora group are also nearly related to the Anatinids. The 

 shell is shaped like the more regular of the Lyonsias, but flattened, 

 especially on the right valve. The hinge is V-shaped, like Placuna, 

 with an internal cartilage, but no ossicle. The valves are pearly 

 within, and with minute prismatic cells outside, of which two hundred 

 and fifty are about as large as one in Pinna. The mantle line is broken 

 as in Saxicava, and scarcely bent, the pipes being very short, separate 

 at the end and fringed. Myodora wants the V~ sna P e( i hinge, and has 

 an ossicle. It is peculiar to the East Indies. 



Family SOLENID^E. (Razor-Shells.) 



We pass on to a very different-looking race of animals, though 

 agreeing in many essential respects with those that have gone before. 

 The .Razor-Fish have the same habit as the Myas, Panopwas^ &c., of 

 burrowing in the sand; only they are created for more rapid move- 

 ments. About two-thirds of the animal consists of the powerful foot, 

 which can be pointed out, or made club-shaped, for the varied necessi- 

 ties of sand-boring, which it accomplishes with such rapidity that the 

 creatures are difficult to catch, burying themselves to a great depth 

 when disturbed. The pipes are very short, and not extended beyond 

 the shell. This is like a piece of pipe cut across lengthways. The 

 Solen may be taken as a good illustration of the ordinary habits of life 

 of bivalves. It stands on its foot, like other animals; but this is the 

 anterior or /ore-end of the shell, the mouth and lips being behind it. 

 The top of the animal is- at the posterior or hinder-eud. of the shell; 

 while the hinge is at the back, and the opening of the valves at the 

 front of the creature, the shells being the side-wings. The length of 

 the shell is from the anterior to the posterior ends, which represents 

 the height of the animal. The breadth is from back to front of the 

 animal; while the height, or thickness of the closed valves, really 

 represents the breadth of the living creature. Solen proper has a 

 straight shell, and one tooth in each valve; while Ensatdla has a 

 curved shell and 2-3 hinge teeth. 



Family SOLECURTIDJE. (Short Razor-Fish.) 



The shells of this group are intermediate between the true Solens 

 and the Tellens. The beaks, instead of being at the bottom end, are 

 more or less near the middle, and the valves are generally flattened. 

 The pipes are separate at the end, and more or less retractile. Sole- 

 curtus proper is like a Razor-shell cut short, while the animal is almost 

 as long; the pipes being united into a stumpy tube till near the end. 

 Novaculina contains the species which live in brackish water, and are 

 covered with a coarse skin. The intermediate species have been called 

 Tagelus. In Cultellus, the shell is flattened and the beaks are strength- 

 ened by a small slanting rib. The pipes are short and separate. Ma- 



