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Show 1882.] 'LIGHTNING' A N D 'PORCUPINE' EXPEDITIONS. 677 Distribution. Off Culebra I. (' Challenger ' Exp.) ; 390 fms. It differs from the young of Fissurella graca, which it resembles in shape, in having not only a different kind of cancellation but especially an internal septum. 1. FISSURELLA GR^ECA, Linne. Patella graca, L. S. N. p. 1262. F. graca, B. C. iii. p. 266, pl. vi. f. 4; v. p. 200, pl. lix. f. 5. ' Lightning ' Exp., St. off the Faroe I. ' Porcupine' Exp. 1870 : Atl. St. Vigo B., 24, C. Sagres, Tangier B.; Med. G. Tunis. Distribution. Shetland (Forbes) to the Archipelago and Egypt, Adriatic, Mogador, Madeira, Canaries; 0-95 fms. Fossil. Miocene: Vienna Basin and Switzerland (Homes) 1 Pliocene: English and Belgian Crags, Transylvania, S. France, N. Africa, Italy, Morea, Rhodes. Post-tertiary : England and Ireland, Sicily, Ischia I.; 0-1360 ft. Varies greatly in the sculpture: in some specimens it is strong, coarse, and sparse; in others fine and close. Very young shells have no foramen or slit, but a prominent spire. I have a monstrosity which grew and lived in the Hamburg aquarium ; after commencing in the usual way, it became expanded and was composed of laminae like those of a common oyster. Linne evidently included several species in his F. graca, as is shown by his citations of Lister, Adanson, and Gualteri. There are several obsolete and questionable synonyms. 2. FISSURELLA GIBBERULA, Lamarck. F. gibberula, Lam. An. s. Vert. vi. (2) p. 15 (1822). ' Porcupine ' Exp. 1870 : Med. St. Benzert Road, Rasel Amoush. Distribution. Brittany to the Archipelago and Egypt, Adriatic, Canaries (McAndrew), Guinea (Dunker), Panama (P. Carpenter); 0-120 fms. Fossil. Pliocene : Italy. Post-tertiary : Sicily ; 0-22 ft. I a m by no means satisfied that this so-called species is more than a dwarf variety of F. graca. Many intermediate forms occur. The size of the foramen and the degree of gibbosity are unreliable characters. Perhaps the present species may have been the long-lost or doubtful Patella pustula of Linne, which is described as " gibboso-con-vexa." The word " praecedeuti" might have been a mistake for " sequenti," viz. to P. graca instead of P.flssura, because the other characters belong to Fissurella and not to Emarginula. However, it is not the F. pustula of Lamarck. F. gibba of Philippi (1836), and a few other synonyms. Gibbus is a classical word, not gibberulus. 3. FISSURELLA NUBECULA, Linne. Patella nubecula, L. S. N. p. 1262; Martini, Conch. Cab. i. t. 12. f. 105. ' Porcupine' Exp. 1870 : Atl. St. Vigo B. |