60 Mr. A. H. Cooke on Vulsella. 



pnblislied, and consequently ■when only six species were 

 known, he says (' Genera/ Vulsella), " On account of the 

 irregularity of the shells in this genus we think it must be 

 extremely difficult to distinguish the species, and consequently 

 we believe that several mere varieties are raised to the rank 

 of species." My own opinion, as will be gathered from the 

 detailed examination which follows, agrees strongly with the 

 view here expressed, and the more so because the number of 

 species since Sowerby's time has been more than trebled. 

 That not a single one of the so-called species of Keeve will 

 bear examination will, I think, be admitted by any one who 

 can appreciate what a variable genus means, for his types can 

 be investigated at the British Museum. Here is a case of a 

 genus whose usual habit is to attach itself to various marine 

 plants, growing with their growth and shaping itself with 

 their shape. The inevitable result of this is a never-ending 

 variation, not merely in shape but in size, colouring, marking, 

 and texture ; and if we pursue Reeve's system to its logical 

 conclusion we shall have as many different species of Vulsella 

 as there are specimens. 



But I go further than merely obliterating the Eeevian 

 species. I hold that two at least of those of Lamarck, viz. 

 spongia^'um and ovafa, are absolutely identical, while the 

 form myti'lma, Lam., constitutes a passage between these and 

 lingulata, from which hians, Lam., differs only in point of 

 size. In the case of an " attached " genus there is not only 

 great variation of shape and size, but it will be found that the 

 less a specimen is attached or imbedded (in sponge, seaweed, 

 &c.) the less irregular it is. Specimens taken from a mass 

 of sponge containing hundreds of shells will be more irre- 

 gular than specimens which occur in less populous or in less 

 confined situations. An instance of this maybe given from a 

 mollusk common on our own shores. The well-known 2'ajjes 

 j}ullastra, L., when in a free state, is as regular in shape, size, 

 and sculpture as any other species of the genus ; but when 

 it occurs in shells, stones, or clay, as the v&nety pe)iforans 

 (and no one has ever seriously disputed the generic identity of 

 the form ^yith. pullasfra) , its shape and texture undergo varia- 

 tions which differ extensively from one another and from the 

 type. The concluding remarks of Eumphius, quoted below 

 under V. lingulata, seem to illustrate this point. 



My impression, formed by the comparison of dozens of 

 specimens with one another, is that the recent species of 

 Vulsella may be reduced to at most three. The free or unat- 

 tached form is the well-known lincjulata, in which the shell 

 not only attains its maximum of size, but develops the 



