586 ME. LINSDALL RICHARDSON ON [Nov. 1906, 



Syn. 1863-64. Dentalium minimum, Tate, pars [the specimens from ChelteuhamJ, 

 Quart. Journ. Geol. Soc. vol. xx, p. 111. 



1870. D. minimum, Tate, ibid. vol. xxvi, p. 398. 



1877. D. minimum, Beesley, Proc. Geol. Assoc, vol. v, p. 183. 



1877. D. minimum, Beesley, Proc. Warwickshire Nat. & Arch. F. C. p. 16. 



1879. _D. minimum, Wright, ' Monogr. Lias Amm.' Pal. Soc. p. 69. 



1882. D. minimum, Slatter (in Wright), ibid. p. 37o. 



1904. D. aff. minimum, Richardson, ' Handbook to the Geology of Chelten- 

 ham ' p. 219. 



Diagnosis. — Shell small, much curved, thin unworn specimens 

 usually exhibiting numerous, extremely- fine, closely-set, transverse 

 linege ; section circular or elliptical ; the shell tapers, especially in 

 immature forms, rapidly from the thicker anterior end to a fine 

 point. 



Remarks. — To the history of this species recorded when dealing 

 with Dentalium minimum (pp. 582-584) it remains to be added 

 that, in the collection of the Geological Society of London, are four 

 specimens mounted on a tablet bearing the words 



' Dentalium parvulum, Buckman. Middle Lias, Leckhampton E-oad Clay-Pits, 

 Cheltenham. E. Tate, Esq., E.G-.S.' 



No description of this species has been published, so far as I know, 

 nor has any figure appeared. 



I think that there can be very little doubt that James Buckman 

 noticed that this form was distinct from Dentalium minimum, and 

 employed the manuscript name of D. parvulum for his own con- 

 venience ; and, when Tate became cognizant of the fact, he agreed 

 with Buckman and recognized his name. At all events, the existence 

 of this tablet of specimens is useful, in that it hints at an idea, 

 never definitely expressed, that the Cheltenham ' D. minimum'' was 

 distinct from the angulata-bed fossil of the same name. 



For some time, I was disposed to think that the forms included in 

 this paper under the name of Dentalium parvulum represented three 

 distinct species. The specimens of this Dentalium from the Valdani- 

 beds have a section becoming slightly elliptical at times, but when 

 this is the case the major axis of the incipient ellipse runs 

 diagonally from (so to speak) the left-hand top part of the section 

 to the right-hand bottom part, and the principal thickening of 

 the test occurs on the dorsal side. Another slightly-different form 

 has typically a noticeable elliptical section, with the minor axis 

 connecting the most widely-separated points on the dorsal and 

 ventral sides, while the principal thickening is at the other two 

 sides, filling in the apices of the ellipse so as to give a circular 

 section interiorly. These two forms, however, pass so gradually one 

 into the other that it really seems inadvisable to separate them — 

 certainly at present. Also, in limestone-beds, the representatives of 

 the species under consideration have relatively a much thicker test 

 and a perfectly-circular section ; but occasionally this character is 

 possessed by examples now obtained from clay-deposits, as at 

 Honeybourne clay-pit. 



Although these three slightly- different forms are perhaps best 

 considered under one specific name at present, it is certainly 



