76 



SUPPLEMENT TO THE 



DESCRIPTIONS OE SPECIES. 



Genus. — Waldheimia, King, 1850. 



1. Waldheimia Mawii Dav. Sup. Sil. Mon. PI. IV, figs. 1, 2, 3. 



"Waldheimia Mawii, Dav. 



Geol. Mag., New Series, vol. viii, p. 145, pi. 

 April, 1881. 



Shell small, marginally subpentagonal, longer than wide, straight, or slightly in- 

 dented in front ; dorsal valve laterally gently convex, longitudinally concave, with a small 

 median rib commencing at about the middle of the valve, and widening as it nears the 

 front ; ventral valve very convex, and keeled along the middle, or divided longitudinally 

 by a groove commencing at about half the length of the shell, and extending to the front; 

 beak small, incurved ; foramen minute, beak-ridges strongly marked ; surface of valves 



smooth. In the interior of the dorsal valve, mider the 

 hinge-plate, a slightly elevated longitudinal septum or 

 ridge extends to within a short distance of the frontal 

 margin ; to the hinge-plate are attached the principal 

 stems of the loop, which, after giving off crural pro- 

 cesses, extend to within a short distance of the front, 

 where they become reflected so as to form the loop. 

 Length 2, breadth 1^, depth |line. 

 Obs. — This small shell was procured by Mr. G. 

 Maw in some abundance from the washings of several 

 tons weight of the " Tickwood Beds," or Upper- Wenlock Shales, from under the railway- 

 bridge at Farley Dingle, also from the upper part of the Wenlock Shale, below Kme- 

 stone ; in water-course, under Benthall Edge, and opposite Ironbridge in Shropshire. 



Having had placed in his hands a number of specimens filled with a hght-coloured, 

 semi-transparent spar, the Rev. Norman Glass was able, after much trouble and patience, 

 to develop the loop in several specimens and in the clearest possible manner ; and so like 

 in general character is this loop to that of Waldheimia that I have, at any rate provision- 

 ally, placed it in that genus. Exteriorly, this small species bears so much resemblance to 

 some forms of Centronella, and in particular to C. Hecate, Billings (' Canadian Journal,' 

 May, 1861, p. 63), that, previously to having been made acquainted with its loop, I had 



Wald. Mawii, Dav. Developed by the 

 Rev. Norman Glass. 



