"Vol. 62. ~] liassic dentaliidj:. 573 



27. Liassic Dentaliidje. By Linsdall Ejchabdsox, F.G.S. 

 (Read March 7th, 1906.) 



[Plate XLV.] 



The Great Western Bailway-line between Honeybourne and Chelt- 

 enham now (1906) nearing completion, necessitated the making of a 

 considerable number of cuttings in the Lias, the zones exposed dating 

 from oocynoti to eapricorniis inclusive. Among the fossils collected 

 were many belonging to the family Dentaliidae. The majority of the 

 forms appeared to be new, and consequently a somewhat exhaustive 

 investigation of the Liassic members of the family was imperative. 

 In the course of these investigations, through the courtesy of the 

 respective keepers, the specimens preserved in the Natural History 

 Museum, the Museum of Practical Geology (Jermyn Street), the 

 Geological Society's Museum (Burlington House), the Sedgwick 

 Museum (Cambridge), and the Bath Museum, have been examined. 1 



Occasionally some difficulty arises in distinguishing the tubes of 

 certain tubicolous annelids of the genus Ditrupa from those of the 

 Dentaliidaa ; but, if the less regular character of the tubes does not 

 suggest their true zoological position, a microscopic investigation 

 will in most cases soon elucidate matters. The shells of scaphopods 

 are of course open at both ends, which is not the case with those of 

 the Serpulidaa. 



It may be of interest to mention that the growth of the scaphopod- 

 shell is effected by means of successive increments at the anterior 

 end, while contemporaneously the posterior end suffers by wear 

 and absorption. The members of this class (Scaphopoda) are essen- 

 tially marine organisms, and for the most part inhabit deep water, 

 being embedded in the mud or sand with only the posterior end of 

 the shell projecting above the surface. There are no littoral species, 

 a ad their food consists principally of foraminifera. 



In this paper it is not purposed to enter into the sub-generic 

 division of Dentalium : the term is employed in the broad sense. 



In the memoir on ' The Lias of England & Wales (Yorkshire 

 excepted),' published by the Geological Survey in 1893, the species 

 of Dentalium recorded from the Lias of this country are : — Dentalium 

 angulation, J. Buckman, D. elongatum, Minister, D. etalense, Terquem 

 & Piette, D.giganteum, Phillips, D. liassicum, Moore, D. limatulum, 

 Tate, D. minimum, Strickland, and D. tenue, Portlock : D. gracile, 

 Moore, D. compression, d'Orbigny, and D. trigonale, Moore, being 

 regarded as synonyms of D. elongatum, and D. PorilocJci, Tate, of 

 D. etalense. The new species made in this paper are Dentalium 

 acutum, D. hexagonale, D. oblongum, D. parvulum, D. suhovatum, 

 D.subtrigonale, D.subquadratum, and D. Terquemi. Moore's D. tri- 

 goaale is found to be a valid species ; but D. tenue, Portlock, and 



1 There are no examples of Dentalia, eitber in the Worcester Museum, or in 

 that of the Royal Agricultural College at Cirencester. 



