MARSHALL: ADDITIONS TO "BRITISH CON'CHOLOGY." 35 



from p. catena in the top of the outer Hp being a little below the 

 spire, the mouth less patulous or more closed in ; it is more tumid 

 generally, and nevers grows so large ; only rarely does it attain a line 

 in length, though I have one from Guernsey a line and a half. 



P. pruinosa Clark. — Guernsey i8f., one specimen; Borough 

 Island, S. Devon; Caldy Island; Loch Linnhe i4f.; Dornoch Frith; 

 E. Shetlands 8-iof. A scarce species. None of the British writers 

 figure this truly, but Forbes and Hanley's is the best. Sars gives a 

 very perfect figure.^ 



P. nitida Jeff. — This species, like P. a7t}^ulata, was almost un- 

 known when " British Conchology " was published, and was recorded 

 only from Skye and Unst. But although still rare, it will be seen 

 from the following records that it is pretty generally diffused on our 

 coasts: — Southport (Heathcote and Chaster) ! Isle of Man (Liv. Mar. 

 Bio. Assoc.)! Aberdeenshire (Simpson)! N. and W. Sutherlandshire 

 (Baillie) ! St. Magnus Bay 6o-8of. (Jeffreys) ; S.W. Ireland io-38f. 

 (R.I. A. cruise) ; Penzance, Cawsand Bay, Eddystone 3of., Babba- 

 combe Bay, Torbay, Pendine, off Southport i2f., Killala Bay, 

 Portrush, Oban 2of., Dornoch Frith. Also British Channel slope 

 69of. and Adventure Bank 92f. ('Porcupine')! off Tunis 50-ioof. 

 (Newport) ! 



I have taken altogether about 70 specimens of this little shell from 

 the above localities. It particularly affects a muddy habitat, and 

 some of the above specimens were dredged almost in liquid mud. 

 The young have a square outline and resemble P. afigiilata of the 

 same size; but this is smooth and glossy, with a larger pillar. From 

 a similar stage of P. apcrta, which is also smooth and glossy, this 

 is more square than round, it is much less open, and the outer edge 

 does not extend beyond the crown. 



P. aperta L. — From Jersey, where it is rare, to East Suther- 

 landshire. 



var. patula Jeff. — Torbay, Weymouth Bay, W. Ireland, and 

 Sutherlandshire. This variety has scarcely any pillar. 



The shell is occasionally solidified by internal layers or pearly 

 excrescences. Several specimens of a curious monstrosity dredged 

 outside the Portland Breakwater has a nipple or spike projecting 

 beyond the crown. 



(To be continued). 



X Moll. Reg. Arct. Norv., tab. i8, figs. 8, Sa. 



