﻿CIRRUS. 



30') 



Cf. for more or less closely allied species — 

 1861. Tukbo Hoenesi, Stoliczka. Hierlatzsch., p. 176, pi. ii, figs. 14, 14 a. 

 1S74. Cieeus Fourneti, Dumortier. Depots Jurass. Bass. Ehone, pt. 4, p. 146, 



pi. xxxvi, fig. 9. 



1878. Sc^vola bus am been sis, Gevimellaro. Faune Giuresi, &c, p. 341, pi. xxvii, 



figs. 1, 2. 



Bibliography, 8fc. — We have now to consider the prevailing forms of Cirrus, 

 which it is convenient to focus under the general term of C. Leachi. The upper 

 row of spiniform tubercles mentioned by Sowerby as noted in the type are rarely 

 seen in specimens, simply because they are not preserved. The type which was 

 obtained at Dundry is now the property of the Bristol Museum. On comparing 

 this fragment with numerous specimens from Coker, Stoford, &c, there can be 

 little doubt as to its substantial agreement with the prevailing forms. 



There is, of course, the usual difficulty about names. When Sowerby's 

 attention was first drawn in 1816 to the sinistral Gasteropods of the Inferior 

 Oolite he named the cast " which was picked up near Yeovil," Cirrus nodosus. It 

 is necessary to put this C. nodosus, No. 1, out of court altogether. First, it is 

 only a cast ; secondly, it was imperfectly diagnosed ; and thirdly, the name 

 "nodosus" was two years later applied by the author to a very different species. 

 I may also remark that the title " nodosus " is applicable to nearly all these shells. 



Thus Sowerby, who had made a complete mess of his genus Cirrus, bequeathed 

 us an evil inheritance in the awkward mixture of names for the two most abundant 

 species. Was it this which led the late Mr. Tawney to state that there was 

 sufficient material in the Bristol Museum to prove the identity of Cirrus Leachi 

 with Cirrus nodosus ? Why did he not go a step further and include Cirrus Calisto, 

 since an excellent specimen of that very distinct form was found on the same 

 tablet? Undoubtedly Cirrus Leachi is the central form which holds out its hand 

 to all the others, but there are many named forms much nearer to G. Leachi than 

 the subdiscoidal species we now recognise as G. nodosus. 



Description. — (N.B. — Since there is so much variety in this species a consider- 

 able margin must be allowed in interpreting proportional dimensions.) 



Leno-th ..... 35 — 40 mm. 

 Height of body- whorl to total length . . 40 : 100. 



Spiral angle (mean) 1 . . . 56°. 



Shell sinistral, irregularly conical, strongly turrited. more or less umbilicated. 

 Spire acute, spiral angle very concave, sutures close* Number of whorls eight 

 to ten ; extreme apical conditions unknown ; the earlier whorls flat, without 



1 The angle is measured so as to include the periphery of the body-whorl. Owing to the concave 

 shape of the shell the difference betweeu the opening of the spiral angle and the mean spiral angle 

 amounts to about 20° in Cirrus Leachi and about 80° in Cirrus nodosus. 



