MARSHALL : ADDITIONS TO " BRITISH CONCHOLOGY." 167 



Truncatella truncatula Drap. — Jersey, Guernsey, and Sark ; 

 Torbay. 



An absolutely smooth specimen is rare. Traces of the longitudinal 

 ribs may generally be seen in the sutural groove or on the shoulders 

 of each whorl. The immature truncated whorls, however, are always 

 smooth. 



Scalaria turtonae Turt. — Scilly Isles, 40 f. ; Doggerbank, 30 f. ; 

 Lancashire coast ; Rum Island, 33 f. Guernsey specimens are much 

 smaller and more slender. 



S. communis Lm. — Jersey, Guernsey, and Herm, at low spring 

 tides, among Zostera. 



This shell is not common in a living state. Dead specimens are 

 frequently cast ashore, but I have never known them taken alive in 

 any number on our coasts. The Torbay form is shorter, broader, 

 and highly coloured. I have a specimen from Liverpool Bay with the 

 delicate ribs of S. pseudoscalaris, but without the encircling keel which 

 distinguishes that species. 



S. trevelyana Leach. — 14 to 100 f., muddy sand. Off Peterhead, 

 58 f. ('Triton') ! Aberdeen trawlers (Simpson) ! Antrim (Chaster) ; 

 Scilly, 40 f. : 30 miles off Whitby, 40 f. ; Rum Island, 33 f. ; Barra, 

 14 — 45 f. ; West Orkneys, 45 f. ; East Shetlands, 25 f. 



The young of this differs from S. clathratula of the same size in 

 being thicker and more conical, with fewer ribs which are angulated 

 at the top, and a deeper suture. The operculum varies according to 

 age, from a light horn colour in the young to almost black in the 

 adult. My largest, from the Doggerbank, are \\ inches in length. I 

 have never seen an adult specimen possessing the top whorls ; they 

 are always more or less truncated. 



S. clathratula Ad. — This species is variable in its proportions ; 

 some slender individuals are only half the width of others. Jeffreys' 

 dimensions are much too large; the usual length is o"25 inch, though 

 exceptional specimens from Guernsey and Laugharne have been found 

 exceeding o - 5 inch, and it was probably one of these that constituted 

 his type. The conditions so favourable to its growth on the Laugh- 

 arne coast are shared by 6". turtonce, specimens thence exceeding two 

 inches in length. A finely ribbed form, which is scarce, has double 

 the usual number of ribs. 



S. pseudoscalaris Brocchi. — Scilly, North Devon, and Pegwell 

 Bay. 1 In the Montagu Collection in the Exeter Museum, two tablets 

 of S. communis have a specimen each of this species, which most 

 probably had a Devonian or Cornish origin. They also appear to 

 have escaped the notice of Dr. Jeffreys, who contributed an article on 



x J. Conch., vol. 5, pp. 190-192, pi. i, f. 4, 1887. 



