138 SHELLS AND SHELL-FISH. PART I. 



which brings us once more to the Strombincp ; and ter- 

 minates the series. We shall now take each of these 

 sub-families in succession, and lay before the reader 

 the result of the closest analysis we have been able to 

 give them. 



(127-) The Strombin^e, or true wing-shells, are obvi- 

 ously the pre-eminent typical group ; and consequently 

 stand at the head of the family. The great expansion 

 of the outer lip in all the genera, save one (^Strombidea*), 

 which connects them to Terehellum, is their best, and, 

 indeed^ their only general, distinction. The genera are 

 five : StromhuSy Sti'ombidea, Rostellaria, Aporrhais, and 

 Pterocera ; all of which are easily recognised. The 

 most typical, perhaps, is Pterocera, where the outer lip 

 is expanded, in mature age, into very long claw-like 

 processes, which gives them something the appearance 

 of scorpions, with the legs, on one side, stretched out, 

 and those of the other concealed ; but their chief cha- 

 racters seem to rest on the basal lobe of the outer lip 

 being turned inwards, and generally toothed. This 

 character, hitherto overlooked, has caused two of the 

 sub-generic types to be placed with the Lamarckian 

 Strombi ; and hence the latter has been overburdened 

 with shells which, we think, do not naturally belong to 

 it. The first, or typical, form is seen in P. lanibis, where 

 the processes of the lip are all pointed in one direction ; 

 and the basal canal, which is considerably lengthened, 

 is curved only on its terminal half. The second is the 

 P. millipeda, — differing from the last, not only in the 

 greater number of the processes, but in those adjoining 

 the spire being more united together at their base ; or, 

 in other words, the divisions are not so deeply cleft. 

 This type prepares us for the third, which has all the 

 characters of Pterocera, except that the lateral pro- 

 cesses are wanting, and the upper are only indicated by 

 deep lobes : the only example yet known, is the shell 

 we formerly figured under the name of Sty'ombus sinii- 



* Represented by Str. urceus and its allies. 



