] 08 MUEIOID^. 



The typical Trophon has a fusiform shell, thin and white, the 

 whorls with numerous, sharp, laminated varices, the interstices 

 smooth, or spirally ribbed; canal open, usually turned to the 

 left; no umbilicus; lip thin, smooth within. This group is essen- 

 tially boreal in distribution. There is, however, another group 

 of species inhabiting the southern temperate and Antarctic zones, 

 which, whilst possessing the main features of the type, the laminae 

 and the white color, present peculiar characters. These shells 

 are usually broadly ovate, shouldered, umbilicate, the aperture 

 dark-colored within. They form a transition to Siphonalia, and 

 might with almost equal propriety be included in that genus. 

 Montfort's definition of the genus Trophon, indeed, does not 

 correspond so well with the typical group as now recognized, as 

 it does with these Siphonalia-like shells. 



Subfamily FTJRPURINM. 



The Muricidse naturally subdivide into two groups, one of 

 them I Murices) distinguished by varices on the shell, operculum 

 with terminal initial point, whilst the other (Purpuras) has nodules 

 but no varices, patulous columella, short canal or mere basal 

 notch, operculum with lateral nucleus ; yet on the confines of 

 these two groups occiir forms which partake of the characters 

 of either, and the classification of which is entirely arbitrary. 

 Ocinebra, species of Trophon, Urosalpinx and Eupleura have 

 undoubted relationships with Purpura, yet are classed with 

 Murex — partly because the species have usually been considered 

 or were described as Murices ; on the other hand. Purpura cria- 

 pata and its allies possess the variceal features of Murex. 

 Kobelt has, on this account, included them in his catalogue of 

 the genus Murex ; but on account of the extreme variability of 

 the species (some specimens being without varices) and the 

 number of connecting forms between the smoother varieties and 

 typical Purpura, I prefer to retain them in the group to which 

 they have usually been referred. 



If the diflSculty of defining these two subfamilies is great, 

 still greater does it become when we descend to the genera and 

 subgenera of either of them. Various authors have attempted 

 it, from the " groups " of Kiener's monograph to the genera and 

 subgenera of H. and A. Adams. I adopt the latter as a mere 

 convenience, premising that nature presents her specific forms 

 here (as frequently elsewhere) in such continuous series, that no 

 real line of demarcation can be traced ; the characters selected 

 represent simply the high tide of an osculation, which at its ebb 

 merges into the next incoming wave. 



Purpura, Bruguiere. 

 Syn. — Mancinella, Link. Microstoma, Swn. Thais, Link. 



