43 Mr. J. G. Jeffreys on British Mollusca. 



one distrust more than ever the limits of definite provinces as 

 laid down by theorists on geographical distribution. It is 

 pretty evident that the once popular theory of the transmission 

 of marine animals (not being pelagic) by means of the Gulf 

 Stream, will not satisfactorily account for the above facts, be- 

 cause that current sets on the ivest of Zetland, and does not 

 impinge on any part of our eastern coasts. As far, too, as the 

 icy current is concerned, it does not flow at all between Iceland 

 and the British Isles. 



The great and startling changes in Geology, arising from the 

 discoveries which have been recently published by Sir Charles 

 Lyell in the Supplement to his ^ Manual,^ show the necessity 

 of continual and extended observation in every branch of science 

 where the materials are not patent or insufficient. While 

 touching on this subject, I cannot admit the inference which 

 has been drawn by Sir Charles Lyell from one of those disco- 

 veries, that, because at certain remote seras distinct natural- 

 history provinces existed on various parts of the earth's surface 

 (evidenced by the remains of animals which had lived during 

 some part of those periods being found imbedded in strata which 

 are supposed to be of contemporaneous formation), therefore 

 there never was a uniform fauna. His own proposition, that 

 present causes were formerly in operation, and which might 

 have effected a disruption of any such uniformity, seems scarcely 

 to warrant the above inference. Whether there ever was a uni- 

 form, or more properly speaking, a universal fauna, it is almost 

 impossible, in the present state of geological knowledge, satis- 

 factorily to determine. 



Acephala LamellibrancMata. 



Pholas Candida, Forh. ^ Hani. Brit. Moll. i. 117. Barmouth. 



Pholadidea papyracea, i. 123. Ballycotton, with Pholas Candida, 

 crispata, and dactylus {Mr. S. Wright, jun.). 



Gastrochaena modiolina, i. 132. Barmouth; in limestone, pro- 

 bably imported from Anglesea. 



Sphsenia Binghami, i. 190. Cork Harbour {Wright). 



Neaera cuspidata, i. 195. Arran Isle, county Galway {Barlee), 



N. abbreviata, i. 201. Skye {Barlee). 



Poromya subtrigona, n. s. PI. II. fig. 1. 



Testa oblique triangularis, ventricosa, insequilatera, antice rotundata, 

 postice latior et subtruncata, solidula, alba, nitida, strigibus trans- 

 versis minutissimis confertis et striis remotis perpaucis versus 

 marginem ventralem notata, intus radiatim striatula; margine 

 antico subrecto ; m.argine postico deciso ; umbonibus prominuHs, 

 minima incurvis; lunula vix distincta; cardine, dentibus, fossa 



