1879.] 'lightning' AND 'porcupine' EXPEDITIONS. 581 



tracted in front : beaks central, but not prominent : cartilage and 

 pit very small, somewhat elongated transversely : hinge-plate rather 

 broad and strong: teeth minute and short, tubercular, 6-8 on each 

 side: inside polished, plain-edged: scars indistinct. L. 0'0275. 

 B. 0-0375. 



" Porcupine ' Exp. 1870 : Atl. St. 2, 3, 3a, 8, 9, Vigo B., 17a, 24. 



Distribution. Palermo and Sciacca ; 113| fms. 



Originally named by me microscopica ; but that word is too much 

 like micrometrica, which has been since used by Seguenza for another 

 species above mentioned. 



22. Leda minima, Seguenza. 



Toldia minima, Seg. Nuc. terz. merid. d'lt. p. 18, t. v. f. 27, 

 27a-c. 



' Porcupine' Exp. 1870 : Atl. St. 3, 13, 17, Ma, 24 ; Med. 55. 



Fossil. Pliocene. Province of Messina. 



The specific name is inappropriate, because this species is not the 

 smallest of the genus Leda. I had provisionally named it subrotunda ; 

 and Monterosato published that name, treating Seguenza's as a syno- 

 nym. 



A. Edge plain or smooth. 



1. Nucula tenuis, Montagu. 



Area tenuis, Mont. Test. Brit. Suppl. p. 56, t. xtix. f. 1. 



N. tenuis B. C. ii. p. 151 ; v. p. 172, pi. xxix. f. 4. 



♦ Lightning ' Exp. : St. 3, 5, 7. 



' Porcupiue ' Exp. 1869: St. I, 6, 9, Galway B., 13, 17. 1870: 

 Atl. 1, 2, 3, 9, Vigo B., 13, 16, 24, off C. Sagres. 



Distribution. Circumpolar in tbe North Atlantic and Pacific, 

 'Valorous' Exp., Iceland to the N.W. coast of France, Mediterra- 

 nean (Nares)\, Maine northwards, Kamptchatka Sea, Vancouver 

 I., N. Japan ; 3-365 fms. 



Fossil. Pliocene and Post-tertiary. Scandinavia, Great Britain 

 and Ireland, Calabria aud Messina, Canada and Maine ; 0-12 ft. 



The arctic form is N. infiata of Hancock, N. antiqua, Mighels, 

 N. expansa, Reeve, and perhaps N- bellotii of A. Adams. In a 

 fossil state the typical form is N. decipiens of Philippi. 



2. Nucula .^egeensis, Forbes. 



N.cegeensis, Forb. Rep. Brit. Assoc. 1843, p. 1 92 : Hanley, Nuculidse, 

 p. 56, pi. v. f. 154. 



'Porcupine' Exp. 1870: Atl. St. 17a, 26-34, 36; Med. off 

 Jijeli, 51, 55, Benzert Road, Adventure Bank, off Rinaldo's 

 Chair, 58. 



Distribution. Mediterranean eastward to the iEgean, Adriatic ; 

 60-250 fms. 



Fossil. Pliocene. Ficarazzi near Palermo. 



Assuming this to be Forbes' s species (although his description is 

 too scanty to be satisfactory), it may be distinguished from N. tenuis 



