574 ME. LINSDALL KICHAEDSON ON" [Nov. I906, 



D. Portlocki, Tate, are probably synonymous with D. minimum, 

 Strickland- Buckman. Probably Dentalium filicauda opalina, 

 Quenstedt, will ultimately be found to be distinct from D. elongatum ; 

 if so, the Liassic species of Bent alia will be seventeen in number, 

 and this without taking into consideration the question as to whether 

 certain varieties of Dentalium parvulum and D. elongatum are 

 sufficiently distinct to rank as species. 



Dextalium acuttjm, sp. nov. (PL XLV, figs. 10 & 11 a-d.) 



Type-localitj' (T.Z.). 1 — Railway-cutting, 'Dixtou West,' near Gotherington, near 



Cheltenham. 

 Horizon (_ET.). — Plienshachian. 

 Hem era (rf). — striati. 

 Collection (Colin.). — L. Richardson. 



Diagnosis. — Shell small, curved, with extremely-fine transverse 

 linese (visible only with the aid of a lens) ; section circular or slightly 

 elliptical; posterior end noticeably acuminate, with a diameter of 

 0-25 mm., and having (for the length of the shell, 3 to 6 mm.) a broad 

 anterior end — the diameter being three times as great as that of the 

 posterior end. Length of holotype =3*9 millimetres. 



Remarks. — On a tablet in the Sedgwick Museum, Cambridge, are 

 ten fossils from the ' Lower Lias, Worcestershire, H. E. S [tricklandl/ 

 One of these is a Ditrupa, another D. cf. elongatum, Miinster, and 

 the remainder probably D. acutum. Pour of the specimens referred 

 to Dentalium acutum are represented (twice natural size) by figs. 11a, 

 b, c, & d, PI. XLY. Certainly the specimens represented by figs. Ha 

 & b belong to this species ; and (although I am not absolutely 

 sure) most probably those represented by 11 e&d do also. Some 

 weeks after the above were examined, I collected from the clay 

 exposed in a railway-cutting near Gotherington, three examples of 

 a form precisely similar to the predominant type in the series collected 

 by Strickland. 



Dentalium parvulum, described on p. 585, is the most closely- 

 related form, but is usually double the length of the present species, 

 attenuates more regularly, and even in the ephebic stage does not 

 show the markedly-acuminate posterior end. Dentalium minimum 

 (p. 582) is much more slender, more erect, and cannot be confused 

 with D. acutum. 



Dentalium angtjlattjm, Buckman. 



T.d. 1844. James Buckman, Murchison's ' Outline of the Geology of Cheltenham ' 



new ed. p. 101. 

 T.f. None. 



1 The letters in parentheses are the abbreviations which will be employed 

 in this paper ; and, for fuller information concerning the use of these and others, 

 the reader is referred to Mr. S. S. Buckman's papers in ' Science ' n. s. vol. xxi 

 (1905) pp. 899-901, and Ann. & Mag. Nat. Hist. ser. 7, vol. xvi (1905) p. 102. 

 It has been suggested to me that the abbreviation for ' Collection,' namely Colin. , 

 is preferable to Coll., since the latter might mean ' collected by.' 



