4 



BEITISH FOSSILS. 



Other Species of the Genus. 



2. In the Museum of Practical Geology there is a head of a small 

 species with a smaller and more pyriform glabella, a wider and 

 more deflected limb (almost involute) in front of it, and a narrow 

 neck segment. It was not found till after the plate was engraved, 

 or should have been added to it. It may be called 



S. INVOLUTA. 



Diagnosis. S. minutus, capite vix 3^ lineas lato, convexissimo, ad 

 frontem decurvo gibbo. Glabella pyriformis^ dimidium capitis cjfficiens, 

 sulcis transversis. Sulci cervicales vix arcuati. Oculi haud remoti. 



The involute limb in front is really about as broad as the width 

 of the glabella, but is so much curved dovm that only a part of its 

 breadth is seen on an upper view. The glabella, not equal to the 

 width of the free cheeks at their base, is pyriform in outline, and 

 marked by two pairs of transverse furrows, which indent it far 

 inward, and one pair, the upper one, which is minute and very far 

 outward. The furrow surrounding the glabella is very sharp and 

 deep, but not broad. It separates an extremely tumid limb, which 

 comprises the broad front margin and the convex cheeks. The 

 facial suture cuts the front margin far outward, as in >S^. primceva, 

 but, unlike that species, it then turns sharply inwards very near to 

 the glabella, and then again abruptly outwards, in a wide curve to 

 what must be the extreme end of the cheek. 



The neck furrow is sharp and deep, and reaches nearly to the 

 end of the facial suture. It is nearly parallel to the posterior 

 margin, instead of curving forwards as in that species. 



The species looks like a dwarfed variety of S. primceva, but is 

 really a very distinct one. 



Locality. — Llandeilo Flags, Newtown Head, Waterford, in the 

 cabinet of Major Austin. 



Explanation of Plate VI. 



Fig. 1, 2. Salteria primceva, Wyv. Thomson; specimens, natural size, from the Cara doc 



schists of Penwhapple Glen, Ayrshire. (Mus. Wyv. Thomson.) 

 Fig. 2 a, 2 b, 2 c. The same magnified. 



J. W. Salter. 



November 1 864. 



