-294 CHASTER AND HEATHCOTE : MOLLUSCA OF OBAN. 



T. barvicensis, Johnst. A number of living and dead speci- 

 mens of this elegant shell dredged. We are unable to 

 consider this as more than a variety o[ T. jnuricatiis^ Mont. 

 Although typical examples, such as our Oban ones, are 

 quite distinct from Guernsey specimens of the last-named 

 species, yet the two appear to be connected by inter- 

 mediate forms which occur at the Isle of Man, a locality 

 lying between the places named. We have very carefully 

 examined specimens from these three localities, and give 

 the results : — - 



OBAN ISLE OF MAN GUERNSEY 

 (i6 specimens). (7 specimens). (6 specimens). 



Average No. of Ribs ii'4 12-5 15 



Range in No. of Ribs ... 10 — 12 12 — 15 14 — 16 



Average No. of Spiral StricC 7 9 11 



Range in No. of Spiral Strise 6 — 8 7 — 11 8 — 13 



Not only do the Manx specimens present gradations in the 

 number of ribs and spiral lines, but also in the character 

 of the sculpture, the spiral lines being sometimes only 

 developed in the flounce-like ribs, as in typical barvicensis, 

 whilst at others they run regularly and continuously round 

 the whorls as in mta-icatus. As regards colour, too, it is 

 worthy of mention that one of the most characteristic bar- 

 vicensis we have from the Isle of Man is tinged with pink. 

 With regard to the slight malacological differences it seems 

 to us that these too may not improbably be merely varietal, 

 an opinion which we hope to have an early opportunity of 

 putting to the test. 



Purpura lapillus, L. Abundant, especially on the rocks at 

 Fraoich Island, where the adult shells are completely 

 covered with Balani. Yellowish-white and white shells 

 predominate, banded ones being rarely observed. 



Trivia europaea, Mont. {Cyprcea europcea). Common on 

 the shore near Kerrera ferry and in some dredgings off 

 Fraoich Island. As is usual in specimens from northern 

 localities all are devoid of spots. A fine series of the 



J.C., vii., Jan. 1894. 



