President's Address. 65 



an oval apci'ture, and long considered as a Murchisonia (M. 

 striahda), but wanting the band and sinus of that genus. 



Under the designation of Euojiiiihalidm, Professor de 

 Koninck has proposed to embrace as a family a most im- 

 portant group of Palaeozoic shells, including the sections 

 Straparolhos, E%tompliahLS, and the like.* The principal char- 

 acters assigned to the family are, a more or less large and 

 open umbilicus, external margin of the mouth furnislied with 

 one, two, or three sinuses, of which the surface of the body 

 whorl retains only the slightest traces, their existence being 

 shown by keels, or imbricating lamella3 of growth, — carae- 

 rated nature of the shell, and the presence of a strong oper- 

 culum. The proper generic or sectional subdivision of the 

 shells, usually known hitherto under the name of Euoinphalus, 

 has caused endless trouble to Palaeontologists. No less than 

 eleven species are said to be found in the Carboniferous rocks 

 of Scotland ; indeed, next to Plcurotomaria, this section con- 

 tains the largest number of species of any Univalve met 

 with in the Carboniferous System. In a paper f published 

 not long ago I endeavoured, to a certain extent, to unravel 

 this confusion, and since then Professor de Koninck, w^ith 

 better material at his disposal, has accomplished the matter. 

 Professor de Koninck regards the various divisions of Euom- 

 phalus and Straparollus as of generic value, whereas I 

 looked upon them merely as sectional divisions of the larger 

 genus, but after carefully perusing his observations, 1 believe 

 his arrangement to be the better of the two. 



The genus proper is Straparollus (De Montfort), containing 

 the conical forms with a large umbilicus, and an oval or round 

 mouth. The Scotch species are S. Diomjsii (De Montf.) and 

 S. pilcopsideus (Phill.) ; the first section is Euomphalus, in 

 which I comprised all those species having a depressed, dis- 

 coid, pentagonal form. On the other hand, De Koninck 

 admits here only those of a similar shape but with a single 

 spiral keel, either in the middle or upper part of the 



* Gasteropodes, p. 81. 



t " Notes on the Gasteropoda contained in tlic Gilbcrtson Collection, 

 British Museum, etc." (Annals Nat. Hist., 1880. v., pp. 473-485; vi., 

 pp. 289-301). 



VOL. Vll. E 



