Manchester Memoirs, Vol. Ixii. (191 7) 109 



otherwise he could hardly have confused his very distinctive 

 types with Schlumberger's. We have not attempted to modify 

 the generic definition of Linderina in order to bring them in. 

 The differences are too wide and deep for reconcilement, and 

 we have found it necessary to institute a new genus for Halk- 

 yard's forms, which we have pleasure in associating with his 

 memory under the name Halkyardia. 



We have had a great advantage in having previously be- 

 come fully acquainted with the structure of Schlumberger's 

 Linderina brugesii in the numerous examples of the species 

 which we identified, described and figured exhaustively in our 

 Selsey Monograph (H-A. & E. 1908, etc. S.B. 191 1. p. 332. 

 pi. XII, figs. 1-7.) We fully confirm the diagnosis of Schlum- 

 berger, which Halkyard disputes. 



The essential differences between Halkyardia and Lin- 

 derina can be briefly explained. In Linderina we have 

 a shell with a horizontal series of planorbuline cham- 

 bers. These chambers by successive thickenings of 

 the external wall eventually result in a bicon- 

 vex disc which, if cut in median section, shows a thick wall in 

 the centre of the disc decreasing in thickness to each edge. The 

 disc is usually somewhat "dished" instead of being symmetri- 

 cally biconvex. In Halkyardia on the other hand the planorbu- 

 line disc of chambers, concave in cross section, tends to fill up 

 the concavity with a mass of shell substance perforated with 

 numerous canals. Seen in section the thickening is confined to 

 the concave side only. Both in shell structure and arrange- 

 ment of chambers, Halkyardia is clearly very closely related to 

 Planorbulina and Cymbalopora.) 



265. [Halkyardia ovata, sp. nov.] 



265A. Linderina ovata, sp. nov. 



PI. VI, figs. 10-12. 



Test depressed, ovate; superior surface slightly convex, 

 inferior surface flat; composed of numerous small chambers, 

 the first four or five of which are arranged in a spiral manner; 

 the later ones disposed on either side of a series occupying the 

 longitudinal axis of the shell. Only the outside row of chambers 

 visible externally. Aperture porous, as in Cymbalopora, or 

 sometimes consisting of one or two larger openings. Length 

 .66 mm., breadth .35 mm. 



