36 HALKYARD, Fossil Foraminifera of the Blue Marl 



pectinate margin (PI. II, fig.ii); second, the comparatively small 

 backward curvature of the chambers (in fact in the weaker 

 forms the sutures are almost at right angles to the longitud- 

 inal axis of the test); third, in some cases the great length of 

 the test in proportion to its width (fig. 13.) 



It will be seen from the drawings given here that the range 

 of form is very great, still, the specimens have all certain 

 features in common which mark them as variations of a single 

 species, and besides this a perfect series can be made up which 

 connects intimately the most dissimilar forms. Figure No. 13 

 is not drawn from a specimen found in the Blue Marl but from 

 one found in the sandy beds (de la Harpe's Zone Superieur) to 

 the north of St. Martin's Point, Biarritz, therefore figures 10- 

 12 may be considered as covering the range of form of the 

 Blue Marl specimens. 



The spiral commencement of the test has been particularly 

 noticed by Schlumberger, who describes the species under the 

 name of Schizophora capreolus, d'Orb., thus reviving the 

 genus created by Reuss. Though he gives the above specific 

 name to his specimens I am inclined to the opinion, judging 

 from the woodcut on page 22, and fig. 4, pi. 3, of his paper, 

 that it is really Batsch's species pennatula which is under 

 consideration. Schlumberger's description is as follows: — 

 "Plasmostracum compressed at the extremities, swollen to- 

 wards the middle ; composed first : of five spiral chambers ; 

 second : of eleven alternate chambers ; third : of four or five 

 simple uniserial depressed chambers. The alternate chambers, 

 as well as the earlier, are separated by prominent sutures which 

 unite on the median line and terminate in a point at the margin. 

 The uniserial chambers are separated by depressions." It will 

 be noticed that this description will apply equally well to 

 B . capreolus or to B. pennatula. 



H. B. Brady also called attention to the peculiar manner 

 of growth of the earlier portion of the test in B. pennatula. 

 He however speaks of it as "occasional" and attributed it to 

 "the extreme backward curvature of the earlier segments." 

 It is evident in that case the chambers would be arranged in 

 pairs surrounding the primordial segment and would not pro- 

 duce the spiral manner of growth plainly seen in Schlumber- 

 ger's wood-cut and my section (PI. II, fig. 12.) 



This species is common at Biarritz. 



(In spite of the foregoing arguments we should be inclined 

 to refer all Halkyard's specimens to Textularia carlnata, d'Orb. 

 There is not a single specimen that could be unhesitatingly 

 referred to B. capreolus.) 



