﻿564 MISS J. DONALD — OBSERVATIONS ON [Aug. 1905, 



26. Observations on some of the Loxonematid2e, with Descriptions 

 of Two New Species. By Miss Jane Donald. (Communicated 

 by Prof. Theodore Groom, M.A., D.Sc.,F.G.S. Read March 8th, 

 1905.) 



[Plate XXXVII pars.] 



The genus Locconema was founded by Phillips in 1841, and was 

 thus described by him : — 



' Spiral, turriculated ; whorls convex, their upper edges adpressed against the 

 next above; without spiral band; mouth oblong, attenuated above, effused 

 below, with a sigmoidal edge to the right lip ; no umbilicus (?) ; surface covered 

 by longitudinal threads or ridges, generally arched.' 



He further states that these observations are merely provisional, 

 until the form of the aperture is more perfectly known. 1 In noting 

 the number of species, he writes that most of them are probably 



'varieties of three or four types having L. sinuosa for one extremity and 

 L. Hennahii for the other ; a second related to L. tumida and L. lincta ; a 

 third to L. rugifera! [Loc. cit.~\ 



Later researches show that this description is correct for the group 

 of shells having Loxonema sinuosum for the type, and the generic 

 name must be restricted to them. The essential characteristics 

 are the possession of whorls adpressed at the suture 

 and the presence of strongly-sigmoidal lines of growth. 

 Shells having more convex whorls, or less sigmoidal lines of growth, 

 must be placed elsewhere. Prof. Koken and other palaeontologists 

 have created several new genera for some of these latter. The type, 

 Loxonema sinuosum, is the first species described by Phillips : it is a 

 Devonian form from South Petherwyn, which he identifies with 

 Terebra (?) sinuosa, Sow. 2 from the Ay meshy Limestone. They are 

 probably distinct species, although Mr. "Whidborne 3 thinks them 

 correctly identified. The striae on the Devonian form are coarser 

 and more raised, as Phillips remarks. Both, however, agree in 

 having the characteristic features of the genus. 



The two new species which I am about to describe resemble the 

 type in form, and in the sinuosity of the lines of growth ; but the 

 whorls, instead of being smooth, are ornamented by spiral striae, two 

 of which frequently stand out and impart to the shell a banded 

 appearance. The specimens that I have seen are not well enough pre- 

 served to show whether the two lines originally were really stronger, 

 or whether this appearance is merely an accident resulting from 

 the manner of preservation. This spiral ornamentation can hardly 

 be considered of sufficient importance, taken alone, to cause their 

 separation from the genus Loxonema ; but, should the discovery of 



1 ' Pal. Foss. Devon, &c.' p. 98. 



2 In Murchison's ' Silurian System ' 1839, p. 619 & pi. viii, fig. 15. 



3 'The Devonian Fauna of the South of England' pt. iii, Monogr. Pal. Soc. 

 vol. xliv (1890-91) p. 176. 



