BY G. I. PLAYFAIR. 543 



Cf. W. & G. S. West, Plankt. Scott. Lochs, Trans. R. Soc. Edin., 

 xli., No.21, p. 4 95. 



The dimensions agree exactly with the Scottish form. The 

 intercalary strips are not present in our specimens, except those 

 that divide the equatorial from the apical and antapical plates, 

 which are sometimes indicated as incrassate ridges(Pl.lv.,figs.8,9). 

 The disposition of the plates in the Scottish form agrees, in 

 general, with that of P. tahulatum var. grare?*Zositm( Pl.lv., figs. 2ft, 

 3c), of which our P. tahulatum var. Westii is certainly an incras- 

 sate variant, specimens having been noted with the membrane of 

 an intermediate character(Pl. Iv., iAf). The ridging, also, of the 

 membrane, in our forms, is more accentuated, straighter, and 

 hardly ramified at all; but, at the same time, I consider the 

 ridged membrane itself so characteristic of this variation, as to 

 outweigh all other differences. The two apical teeth of var. 

 granuloaum are sometimes present. 



Var. ZONATUM, n.var. (PI. Iv., figs. 10-1 2). 



Forma glotiosa; fossa transversa centrali; membrana glabra; 

 tabulis wquatoriis omnibus taeniis rectis parallelis incras.satis binis, 

 transverse dispositis, ornatis; tabulis apicalibus antapicalibusque 

 vulgo confusis, membrana ut in var. Westii. 



Long. 5i; lat. 50-59 //.. 



Filter-samples, 100, 102, 115. 



The connection of the three foregoing forms with one anothei- 

 and with P. tahulatum, is well shown by the figure in Pl.lv., i.^h. 

 The shape and tabulation, both front and hack, are those of /'. 

 tahulatum; the marking of the membrane, in general, is that of 

 var. yrauidosum; while at x, there is a distinct transverse ridge 

 as in var. zonattim, and here and there, especially just below the 

 transverse groove, are clear traces of the longitudinal ridges of 

 var. Westii. 



Var. HiEROGLYPHicuM, n.var. (Pl.lv., f.l3). 



Forma globosa; fossa transversa centrali; membrana glabra; 

 tabulis aequatoriis solis formatis, notis hieroglyphicis disjunctis 

 ornatis. Zonis intercalaribus latissimis, rugis incrassatis paucis 



