48 Mr. W. Clark on tlie Skeneadse. 



greater rapidity of locomotion. I fully expect to examine the 

 Skenea nitens, and perhaps the Adeorbis subcarinatus. — W. C. 



Since the above was written, my expectation respecting the 

 S. nitens has been verified by the occurrence of three live speci- 

 mens, I have thus had the singular satisfaction of contempo- 

 raneously examining three rare unrecorded creatures ; — I almost 

 think a similar concatenation will scarcely again occur to any 

 naturalist : — 



Skenea ? now Trochus, nitens, nobis ; Trochus pusillus, auct. 



The same difficulty in distinguishing the specialties of this 

 species from those of the two preceding ones exist. I can only 

 say, that the tentacula and vibracula may be less long in propor- 

 tion, the foot shorter, broader, and more rounded in front and 

 behind, with the curved auricles more free or less attached to 

 the anterior line of the foot, being only amalgamated with it by a 

 broadish central lobe of union, than in either of the others ; the 

 eye-pedicles may also be more pronounced than in T. serpuloides, 

 but less so in T. Cutlerianus. I never saw three animals so similar, 

 malacologically, with the hard parts so decidedly differing in 

 most respects. 1 may say that this species has four lateral 

 vibracula, and it is possible the other two may have the same 

 number. In these very minute beings, from the continual change 

 of position, we cannot always arrive at facts with certainty. My 

 own impression is that all of them have four vibracula ; but how- 

 ever this may be, in a generic point of view it is of no moment. 

 This is the minutest animal of the three, and by far the most 

 active ; thus again showing, as I formerly observed in the ' An- 

 nals,^ on Ccecum glabrum, that nature, as she diminishes in volume, 

 usually accompanies that condition with an equivalent of inci-eased 

 energy and activity. 



And finally, in addition to the three species just noticed, I 

 give a list of others I have examined, the animals of which I be- 

 lieve are all unrecorded ones, and will be communicated when 

 the minutes are reduced to order. 



Cheni. Sandvicensis. 



C. decussata. 



C. elegantissima. 



C. pusilla : very distinct ; not a var. of C elegantissima. 



Rissoa costata. 



R. soluta. 



R. reticulata ; Beanii, nonnuU. 



The two following may have been mentioned, but perhaps 

 fuller accounts will be acceptable, 



Rissoa inconspicua, Alder. 



Conovulus bidentattis ? 



