28 



SUPPLEMENT TO THE 



the hinge-plate, and that at the point where the two lamellae composing the loop join 

 there is a short bifurcation directed upwards. In this latter respect the loop of Bifida 

 resembles that of Wldtfieldia. A comparison of the accompanying figures of Bifida 



with those of Meristina and Wldtfieldia, given 

 in the Silurian Supplement, will show the 

 above points of resemblance and difference. 

 The loop of this species being new I have 

 given to it the generic name of Bifida^ 

 in allusion to the forked extremity of the 

 loop. 



Mr. Whidborne informs me that B. lepida 

 occurs in the Middle Devonian at Hope's Nose, 

 near Torquay, and that it is remarkable how 

 separate the specimens of B. lepida and 

 Kayseria lens are from each other in that locality. In the upper beds, where he has 

 found more than fifty specimens of B. lepida, he has only found one of K. lens. In the 

 lower beds in the same locality, where he has found K. lens to be common, he has not 

 seen a single specimen of B. lepida. He says that the specimens of B. lepida occur 

 in one spot a few yards long, so that this species would appear to have been gregarious 

 whilst the specimens of K. lens are scattered evenly along the bed in which they are found. 

 It is very uncertain whether B. lepida has been found at Lummaton. The specimen 

 in Mr. Lee's collection that had been referred to this species is in all probability a 

 worn example of B. Huntii. 



Bifida lepida. 

 1. Ventral aspect. 3. Dorsal aspect. 

 Developed by Rev. N. Glas 



Enlarged. 



15. Bifida Hdntii, Dav. Dav., Dev. Sup., PI. I, figs. 17, \la, lib, 18. 



Shell small, circular, about as broad as long; valves almost equally deep and mode- 

 rately convex. Dorsal valve somewhat depressed and longitudinally divided by a small 

 narrow rib. On either side are two large rounded ribs with interspaces of about equal 

 breadth. Ventral more convex than the dorsal valve, and longitudinally divided by a 

 narrow groove. On each of the lateral portions of the valve are two large rounded ribs 

 with wide interspaces. Beak small, very slightly incurved. Surface crossed with 

 transverse lines, similar to those in B. lepida, but more numerous and finer. 

 Length 3^, breadth 3^, depth 1 line. 



Ohs. — Several specimens of this small species have been found by Mr. Whidborne 



