Description of Genera and Species. 25 



dites are seen just beyond the riyht margin of the carapace. The sternite of the first 

 tail segment indicates that the bases of the pleopods were not placed so far apart as 

 those of the adjacent trunk limbs. 



Locality. — Whiteadder Water, near Duns, Berwickshire. 



Horizon. — Cementstone Group (Tuedian), Scottish Calciferous Sandstone Series. 



Collector. — A. Macconochie. 



Tealliocaris kobusta, var. nov. PI. III. fii^s. 9-12. 



Specimens of a smaller and more slender form, that may be considered as a variety 

 of this species, were once suljmitted to me for description by the late Mr. Coutts of 

 Glasgow. At his death they were acquired by the Royal Scottish ]\[useum, Edinburgh, 

 and now form part of that collection in Edinburgh. 



General Description. — The inside view of the carapace of one of the specimens is 

 shown, natural size, in fig. 10, the outside of the right half, also natural size, in 

 fig. 11. From these, it is apparent that it agrees with the carapace of the parent species 

 in the arrangement of the longitudinal keels, in the blunt spine at the antero-lateral 

 angles, and in the backwardly-directed peak in the mid-line of the posterior margin. 

 On the other hand, it differs from it in general form, being narrower and longer 

 proportionately, in the keels and lateral margins being either smooth or only so slightly 

 crenulated that this feature has escaped detection, in its narrower rostrum, and in 

 being more hollowed out behind. The carapace exhibits the same tendency to split 

 along the mid-line as that of T. rolnista, and, like it, to show its interior aspect. This 

 latter point is worthy of notice, for it is evidently owing to the very prominent keels 

 and the rough pitted integuments of the dorsal side giving it a greater hold of the 

 embedding rock than the smooth inner side, tliat, when the rock is split open, the break 

 takes place along the inner side of the fossil. 



Part of the carapace and the greater part of the tail are shown natural size in fig. 9, 

 and the last segment and tail fan, magnified four diameters, in fig. 12. These all agree 

 with generally corresponding parts in the parent form, but the proportions are slightly 

 different. The nature of the ornamentation of the embossed parts of the test is the 

 .same ; but the crenulations on the crests of the ridges are either absent or inconspicuous 

 in the present form. It is perhap.s worth observing that the telson shows the 

 characteristic terminal lobe and the accessory swimmerets, broken away in specimens 

 of T. rolnista. 



Remurks. — Tlie specimens from which the characters of this variety have been 



D 



