40 



as high as the diameter of the valve. From this the beak 

 is bent down, and small. The specimen described, which 

 was attached to the shell of a pinna, has the summit in- 

 flated and round ; but a specimen which I found in 

 Mount's bay attached to sea-weed, was about equally 

 elevated but pointed. Further research will decide 

 whether these specimens belong to the same species. In 

 another specimen, found with the former in Mount's bay, 

 the beak approached but did not join the margin ; and 

 the upper valve was characterized by a number of well 

 marked circular raised ribs. 



BRACHIOPODA. 

 The shell bivalve, adhering either directly or by a tendi- 

 nous cord. 



TEREBRATULA. 

 GENERIC CHARACTER: Shell with valves unequal, 

 regular, subtriangular, attached to bodies by a short ten- 

 dinous pedicle; beak of the larger valve produced, often 

 curved, perforated at the summit ; hinge with two teeth ; 

 two nearly bony, slender, elevated, forked, variously 

 branched processes rise from the disk of the small valve, 

 and support the animal. 



I found the toothed valve of what I believe a species of 

 this genus, at Par : but the precise species is uncertain. 



CLASS IV. 

 MOLL USC A, 



The body sometimes naked, either destitute of any solid 

 internal parts, or inclosing a shell or other hard substance, 

 and sometimes provided externally with a shell covering or 

 sheathing, but never composed of two opposite valves united 

 by a hinge. 



The distinguishing character of the Mollusca is, that they 

 have no vertebrae, are wholly without articulations, and have 

 a more or less prominent head at the anterior part of the 

 body. Their instincts are more developed than any of the 

 species already enumerated. 



PHYLLIDIANA. 



Some have no shell, either within or without; others are 

 wholly or in part covered by a shell, sometimes composed of 

 one single piece, sometimes of a range of moveable and 

 distinct pieces. 



CHITON. 



GENERIC CHARACTER: Shell formed of separate 

 pieces, in number from eight to six, fastened together 



