1883.] 'lightning' AND 'porcupine' EXPEDITIONS. 103 



the Adriatic; 0-20 fms., living in the littoral and lamiaarian 

 zones. 



Fossil. Pliocene : Tuscany. Post-tertiary ; Cumbrae, Ireland, 

 Cheshire, Shropshire, Hants, and Dorset. 



T. umbilicavis. Pennant (not Linne), T. umbilicalis, Da Costa, 

 and other synonyms. T. oblique radiatus of Chemnitz or 2'. ob- 

 liquatus of Gmelin is most probably T. divaricatus of Linne, if 

 indeed the last-named species be distinct from the present. Should 

 they prove to be identical, my view that the Mediterranean has no 

 peculiar Molluscan fauna would be further confirmed. See the Report 

 of the British Association for 1873. T. divaricatus of Gmelin is 

 evidently Lacuna divaricata, although he gives the habitat in his 

 usual muddled way, viz. " mari mediterraneo et groenlandico." The 

 umbilicus is either open or closed, as in T. divaricatus. I subjoin a 

 description of the animal of var. agathensis {T. agathensis, Recluz), 

 which has no umbilical perforation. 



Body greyish-white or soot-coloured, closely streaked lengthwise 

 with purplish-brown, sometimes having a yellow tinge : mantle 

 thick, with large lobes or lappets, sulphur-coloured ; the lobe on the 

 right hand is scalloped, the other having plain edges and folded : 

 snout thick and rather short : tentacles filiform, club-shaped at the 

 tips, thickly covered with short cilia, and ringed with purplish- 

 brown : eyes globular, placed on angular offsets at the outer bases of 

 the tentacles : foot oblong, rounded or bluntly pointed at each end; 

 sides closely tessellated or reticulated by purplish-brown lines, 

 with occasionally a few white specks ; edges fringed with numerous 

 clavate points arranged in a single row ; sole pale lemon-coloured : 

 appendages three on each side, resembling the tentacles in shape, 

 but somewhat shorter. Inhabits the lower part of the tide-mark 

 throughout the Channel Isles, the ordinary or typical form occupying 

 the higher part, and both forms (as well as an intermediate one) 

 being found halfway. It crawls like Littorina, by an alternate wave- 

 like motion of each side of the foot. 



1/ 23. Trochus divaricatus, Linne. 



T. divaricatus, L. S. N. p. 229 ; Philippi, Conch. Cab. ed. 

 Kiister, t. 29. f. 16. 



♦ Porcupine ' Exp. 18/0 : Atl. St. Gibraltar B. 



Distribution. Atlantic coasts of France (Petit)!, N. Spain and 

 Portugal (Mc Andrew) , Mediterranean, Adriatic, and Black Sea ; 

 0-15 fms. 



Fossil. Post-tertiary: S. France (Fischer). 



The umbilicus is perforated in the young and closed in the adult. 



T. rarilineatus of Michaud is a variety of this species according 

 to Monterosato. 



24. Trochus TRiCARiNiFER, (^ncarmz/erMs) Searles Wood. 



T. iricariniferus, S. Wood, Crag Moll. 1848, p. 132, t. xiv. 

 f. 6, a-b. 



'Porcupine' Exp. 1870: Atl. St. 16. A single specimen 

 Prog. Zool. Soc— 1883, No. VIII. 8 



