180 DEVONIAN FAUNA. 



convexity gradually increasing on the sides, the extremities of which meet the 

 hinge-line at an obtuse angle. Ventral valve moderately convex. Dorsal valve 

 flat, becoming concave near the margins. Hinge-line with (at least) two very 

 long, thin, slightly oblique spines on each side in the ventral valve. Surface 

 covered with multitudinous elevated, rounded, divaricating and sometimes rather 

 flexuous, minute radiations (probably about 150). 



Size. — A distorted specimen is 8 mm. long by 15 mm. wide. 



Locality. — In the Porter Collection are two slabs, containing several specimens 

 from Pilton or Fremington. 



Remarks. — These fossils appear distinguished by the very great number of 

 the ribs, as well as by the flexuosity of these ribs, which seems to be caused by 

 their frequent divarication at irregular intervals. 



They are very similar to Chonetes Dalmaniana, de Koninck, 1 as given by 

 M'Coy 2 and Davidson, 3 but appear to differ by their longer, less oblique, and 

 (apparently) fewer hinge-spines, and their rounded cardinal angles. 



As far as can be judged from Meek and Worthen's figure, they do not appear 

 distinguishable from Oh. Illinoisensis, though in that figure the length of the 

 spines is not shown, and the sides of the shell seem rather straighter. 



2. Order— INARTICLTL ATA, Deshayes, 1836. 



I. Family — Cranud/E, d'Orbigny, 1847. 



1. Genus — Cuaniella, CEhlert, 1888. 



1. Crania insecura, u. sp. Plate XXII, fig. 9. 



Description. — Cast of dorsal or upper valve irregularly quadrate with 

 rounded angles, rather longer than broad, and widest at or about one-third the 

 diameter from the front. Apex small and sharp, slightly in front of the centre. 

 Contour broadly conical, but having two large indistinct swellings before the 

 apex, one on each side, in front of which the surface sinks steeply to the margin. 

 Anterior margin almost straight ; lateral margins oblique and slightly arching ; 

 posterior margin straight, and only half the width of the anterior. Margins (in 

 cast) with a broad concave border. Occlusor muscle-marks two, concave, ovoid 



1 1843, de Koninck, 'Discr. Anim. Foss. Terrain Carb. Belg.,' p. 210, pi. xiii, fig. 3; and 

 pi. xiii bis, fig. 2. 



2 1844, M'Coy, ' Synops. Carb. Foss. Irel.,' p. 119, pi. xx, fig. 7. Mons. CEhlert informs me that 

 he questions the identity of M'Coy's and de Koninck's species. 



3 1861, Davidson, 'Brit. Foss Brach.,' vol. ii, pt. 5, p. 183, pi. xlvi, figs. 7 — 7 b. 



