ASPERGILLUM. 



external characters and form. Another error, however, 

 has arisen, and has been commonly adopted by English 

 collectors, which it is equally necessary to correct : this 

 error consists in supposing* that ihe animal buries its shell 

 partly in the sand, exposing the larger fimbriated extremity 

 with a small hair-like fleshy tube passing through each 

 little shelly tuhe of the fringe, giving it the appearance of 

 an expanded flower standing up Qut of the sand. That 

 the animal partly buries its shell in the sand, we know 

 from certain information to be true, and that small tubu- 

 lar folds of the fleshy mantle line each of the little tubes 

 that form the fringe is also probable, but the fact for which 

 we contend is, that the larger fimbriated extremity is buried 

 in the sand, and that the smaller open end, which must 

 contain the respiratory and excretory tubes of the animal, 

 is alone exposed, and this we think is proved by its ana- 

 logy with all other 'TidncoUes, and particularly with Cla- 

 vagella^ which we have already published. 



The very unusual structure of the shells which com- 

 pose this Genus renders it a difficult task correctly to de- 

 fine its characters, we have, however, endeavoured to ren- 

 der the following concise description as clear and correct 

 as possible. Shell consisting of two equal sized nearly 

 equilateral valves, open at both ends and closely soldered 

 to the inside, near the lower extremity of a clavate shelly 

 tuhe, so that the umbones pass through the tube and are 

 exposed, being rather prominent, on the outside of the 

 tube ; the anterior and lower end of the tube, of which the 

 whole apparent shell consists, is in a great measure closed 

 by a terminal disk which is all over perforated by nume- 

 rous, minute, externally prominent pores ; it has a small 

 central fissure, and is generally surrounded by a marginal 

 fringe composed wholly of small tubes, sometimes branch- 

 ed, but more frequently simple; the upper end of the 

 principal tube, which is posterior, is elongated, more or 

 less attenuated, and open ; its margin is sometimes re- 

 flected and undulated : this open end is so commonly im- 

 perfect in the specimens that are brought to Europe, that 

 it is impossible for us to ascertain whether the last cha- 

 racter be constant or not. Some of the species attach 

 grains of sand and small shells to the outer surface of 

 their tubes. 



The Genus Aspergillum is so easily distinguished from 



