1883.] 'lightning' AND 'porcupine' EXPEDITIONS. 107 



Distribution. Finmark and Faroes to the Morea and Egypt, 

 Adriatic, Mogadon, Madeira, Canaries; 0-85 fms. 



Fossil. Miocene: Vienna Basin, and Marne Vaticano. Pliocene: 

 English and Belgian Crags, Italy, Rhodes. Post- tertiary : Scot- 

 land, Ireland, S. France, Leghorn. 



Var. conulus. Smaller and more conical. 



T. conuhis, L. S. N. p. 1230 ; Forbes and Hanley, pi. Ixxiii. f. I, 2. 

 With every inclination to retain a Linnean species, I have endea- 

 voured, but failed, to distinguish specifically T. conulus from T.zizy- 

 phinus. Indeed Linne admits that the former is probably a variety 

 of the latter: — "Testa sequenti (sc. T. zizyphino) simillima ut fere 

 varietas minima, etiam apice tuberculata, sed linea inter anfractus 

 promiuula ; color pulcherrime variegatus. " 



The number of synonyms is a great disgrace to naturahsts. I 

 find 23 of them, besides at least a dozen more as species described 

 by Risso. See also ' British Conchology,' vol. iii. pp. 332 & 333. 



Extremely variable as to size, height of the spire, colour, sutural 

 ridge and other sculpture. The apex is always more or less granu- 

 lated, even in the smoothest variety or T. lavigatus of Phihppi. 

 Very young shells have a small umbilicus. 



y 33. Trochus occidentalis, Mighels and Adams. 



TrocJius occidentalis, Migh. and Ad. Proc. Boston Soc. Nat. Hist, 

 i. p. 47, pl.iv. f. 16 : B. C. iii. p. 333; v. p. 204, pi. Ixxiii. f. 7. 



♦ Lightning ' Exp. St. 2, 5. 



'Porcupine' Exp. 18G9 : St. 6, 25, 61, 68. 



Distribution. Finmark and Faroes to the Dogger Bank, eastern 

 coasts of North America; 8-150 fms. 



Fossil. Pliocene : English and Belgian Crags, Messina. 



T. alabastrum. Beck ap. Loven, and T.formosus, Forbes. 



In elucidation of the habits of this Trochus mentioned in ' British 

 Conchology,' iii. p. 335, Mr. Buchanan says in his paper on the air 

 dissolved in sea-water (Proc. R. S. Edinburgh, 1877) : — " As regards 

 the percentage of oxygen present at different depths, it diminishes 

 from the surface to a depth of 300 fathoms, and increases from that 

 point to lower depths." The odontophore of this and other Scan- 

 dinavian species has been figured by Friele. 



I have also fragments of two or three species of this section, 

 besides very young specimens of other species of Trochus, from the 

 ♦ Porcupine ' Expeditions, none of which I have been able to identify 

 with any known species. 



Olivia otaviana, Cantraine. 



O. otaviana, Cantr, Diagn. esp. nouv. de Moll. (Bull, de I'Acad. 

 Brux. ix. 2, 1835), p. 12; Mai. Med. t.vi. f. 13. 



• Lightning' Exp. St. 6. 



♦ Porcupine ' Exp. 1869 : 14, 89. 1870 : Atl. C.Sagres, 24, 27. 28, 

 28 a, 30, 36 ; Med. 45, Capo di Gaeta, Adventure Bank. The spe- 

 cimens are young or mostly fragmentary ; but many of them are 



