CYRTOCERAS. 109 



those in the British Museum would probably solve this question, though our 

 Devonshire material is not enough for final identification. 



C. suhconicum, Sandberger, is said by him to be the same as C. lineahim, 

 Goldf. Its section seems more definitely triangular than the English specimens, 

 and I am not sure of its identity. Why he changes Goldfuss's name does not 

 appear. 



G. nmltiseptatmn, F. A. Romer, appears also to be a synonym. 



Affinities. — G. depressum, Goldf., as given by d'Arch. and de Vern.,^ has a more 

 flattened dorsal side, and consequently a more triangular section. PhrcKjmo- 

 eeratites suhventricosus, d'Arch. and de Vern.,^ is a still larger species with a very 

 elongate, elliptic section. In both cases the siphuncle is marginal. 



Perhaps Phragmoceras eximium, Eichwald/ is most like the Lummaton fossil, 

 chiefly differing in the sections being more elongate. 



6. Cyrtocbras Robertsii, n. sp. PI. XI, figs. 9, 9 a, 9 b, 9 c. 



Description. — Shell small, tapering rather rapidly, slightly recurved. Section 

 sub-circular, rather asymmetrical. Septa concave and distant ? Ventral outline 

 convex ; dorsal outline slightly concave ; lateral outlines unequally oblique. 

 Siphuncle central ? or close to ventral margin ? Surface covered by crowded 

 microscopical transverse stride, slightly looped backward over the ventral line, 

 and with occasionally one larger than the others. 



Size. — Length without apex, 45 mm. ; greatest width, 22 mm. 



Localities. — One specimen in my Collection is from Lummaton, and two defec- 

 tive specimens from Wolborough, apparently belonging to the same species, are 

 in the Museum of Practical Geology. 



Remarks. — This species, as shown by my specimen, seems distinguished by 

 its regularly tapering and slightly recurved and asymmetrical form, and I am not 

 aware of anything resembling it described by foreign authors. 



The position of its siphuncle is doubtful. At the apical end it appears to be 

 central, but at the upper end there is an appearance that might indicate it to be 

 marginal. I am very doubtful whether the latter appearance is not delusive, 

 although at the time of drawing the plate we thought it sufficiently clear to 

 indicate it in the section fig. 9 h. 



1 1842, D'Arch. and de Vern., ' Geol. Trans.,' ser. ii, vol. vi, pt. 2, p. 350, pi. xxix, figs. 1, 1 a. 



^ Ibid., p. 351, pi. XXX, figs. 1, 1 «. 



•^ 1860, Eichwald, ' Leth. Eoss.,' vol. i, p. 1274, pi. xlvii, fig. 2. 



