54 DEVONIAN FAUNA. 



BemarJcs. — Although this fine Ostacod occurs not infrequently, it is very 

 difficult to get a specimen showing all the characters of a valve at once, and I have 

 hitherto never obtained the two valves in apposition, although in two or three 

 cases they have been found together. At the same time it is a very well charac- 

 terised fossil, and easily distinguishable from any of the other organisms of the 

 quarry whence it comes. Since my friend Prof. Rupert Jones founded the 

 species on specimens which I sent him in 1880, I have met with numerous other 

 examples, but none which give much more information about it, and consequently 

 the description here given has been copied to a large extent from his original 

 description. 



The muscle-spot approaches one condition of that of Bntomoconchus, as 

 figured in the ' Monograph of Garb. Cypridinadse,' Pal. Soc, 1874, PI. I, fig. 4, cZ, 

 but in the latter the radiating lines are much more symmetrical, and the middle 

 portion not so reticulate. 



The specimens difi'er considerably in the amount of their convexity and in their 

 size, but otherwise, as far as can be judged, they do not vary much. 



To one of the valves of this species in my possession is attached a tiny parasite, 

 not more than 1 mm. in length. In shape it is the half of a prolate spheroid, 

 and is smooth, but beyond this I can discover no characters, even through the 

 microscope. It probably is a larval form. 



SeDIS INCEETiE. PI. IV, figS. 19 CI, 19 h, 19 c. 



Description. — Univalve, extremely convex. Outline of the open base oval, with 

 a raised margin along part of the edge. Surface apparently smooth, with the 

 exception of two unequal tubercles some distance above the margin on one side. 

 Longitudinal outline of elevation nearly semicircular. 



Size. — 17 mm. in length. 



Locality. — Lummaton. 



Bemarlcs. — The specimen here described was at first thought to be a Cyclus, 

 and as such was here figured, but it is now supposed more probably to be the 

 injured remains of some Gasteropod such as Naticella, the hinder and higher 

 tubercle being taken to give the indication of a spire. It is in a most unsatisfac- 

 tory state of preservation, the surface is defaced, and the nature of the matrix is 

 such as to render it almost impossible to distinguish it from the fossil itself. There 

 are therefore no data for deciding its true position until the discovery of a better 

 specimen. 



