DITHYROCARIS GLABRA. 139 



miual segments (ultimate and penultimate) and a caudal appendage of three stout 

 sharp spines, smooth but finely fluted. These have a reversed position, so as to 

 intrude into the postero-dorsal region of the valve. 



The middle spine (style) is obscured at its extremity, but seems to have been 

 about as long as the others. The lateral or outside spines (stylets) are each 

 about 25 mm. long. 



As with fig. 2. Lower Carboniferous ; East Kilbride. 



PI. XIX, fig. 4. Brit. Mus. No. 59541, No. 28. 



Characters. — This figure shows a smooth impression (on black shale) of the 

 posterior ends of two valves, somewhat displaced. The fringed or serrated 

 hinder part of the ventral border in each valve is distinctly visible. The 

 test of two abdominal segments remains, but broken by pressure; also the 

 proximal portions of three relatively broad caudal spines, crushed and displaced. 



Size. — The penultimate segment is about 5 mm. long; the ultimate segment 

 about 10 mm. long, and about 7 mm. broad in its crushed condition. 



Black shale, slightly calcareous. Lower Carboniferous; Ardross. 



This is one of the specimens of D. glabra exceedingly abundant at Ardross or 

 Ardross Castle. Our friend Mr. J. W. Kirkby informs us that " Ardross " and 

 " Ardross Castle," in Fife, refer to the same locality. The beds containing the 

 Dithyrocaris and other fossils are bounded on each side by volcanic ash, so that 

 their exact position in the Carboniferous series is rather doubtful ; but they are 

 now mapped by the Geological Surveyors as Calciferous Sandstone, and he thinks 

 they are in that division, probably somewhere near the top. 



PI. XXV, fig. 1. Brit, Mus. 59541, No. 6. 



Characters. — These two valves, squeezed sideways together, one over the 

 other, and retaining some considerable convexity, are about 38 mm. in width (the 

 carapace when perfect was probably 50 mm. wide and about 55 mm. long). 



The dorsal edge of the right valve overlaps the dorsal region of the other 

 valve. There is present an imperfect dorsal crest (broken at each end, but still 

 20 mm. long), which has been shifted so as to have its right edge between some 

 (intruded) shale and the overlying dorsal edge of the right valve, while its left 

 edge rests on the dorsal region of the left valve. The disturbance that the valves 

 have suffered unfortunately hinders the former relationship of the parts to be 

 quite so plainly understood as in the next example (fig. 2). 



From black shale, slightly calcareous, East Kilbride. 



PI. XXV, fig. 2. Brit. Mus., No. 8. 



Characters. — This left valve, 48 mm. long and 25 wide, has some of its dorsal 

 crest still attached to its dorsal region. The fragment consists of the front 



