PnOLADIDEA. 127 



the Clip and membrane. The cup we consider as nothing 

 more than an incipient shelly lining of its habitation for the 

 protection of some part of its tubes, probably the ciliated 

 orifices, which are more complex in this species than in any 

 of the others, and is, in some measure, analogous to the 

 shelly linings of the Teredo and Gastrochoena. An inspec- 

 tion of the tubes of the animals which are precisely similar, 

 and which differ most conspicuously from all the other 

 Pholads, will at once convince the most sceptical of their 

 identity. The orifices of the two tubes are placed in a dis- 

 tinct finely-fringed circle, unlike in this to all our other 

 PJiolades. The branchial tube has around its orifice twelve 

 rays, with a smaller one between each. The upper or anal 

 tube is plain and closely united to the lower, and both are 

 placed within a finely white-fringed circle. The tube is 

 pale reddish brown to within about a quarter of an inch of 

 its extremity, where it is of a pearly white. The rays and 

 orifices within the white-fringed circle are pale reddish 

 brown. The foot is small, oval, and somewhat pointed be- 

 fore and behind. The belly of the animal is white, mot- 

 tled with intensely white flaky points or dots, as in PJiolas 

 candidal 



Plioladidea papyracea must be considered not only a 

 very local shell, but one difficult to procure even at most of 

 the spots from whence only it can be obtained. It is met 

 with at very low tides imbedded in reddish sandstone 

 {Trias) at Exmouth, Teignmouth, Torquay, and other 

 towns of the South Devon coast ; but its extreme fragility 

 renders its safe extraction, and the subsequent removal of 

 the animal matter, a work of delicate manipulation. The 

 dwarf variety we have figured was dredged some five 

 or six miles from land in lumps of indurated red clay, by 

 Mr. Clark, of Exmouth. Portrush, in the north of Ire- 



