172 HRITISH PALAEOZOIC PHYLLOCARIDA. 



the dorsal and the neighbouring thin parallel ridge ; and a thin layer or film on 

 the rest of that part of the test allows the blunt little prickles to be recognisable, 

 and leaves bare the anterior fourth part and some of the posterior surface. 



On the outer division of the right valve a narrow thick layer of the black 

 shale lies between the mesolateral ridge and the ventral border. The latter here 

 shows the impression of a narrow rim, marked with very fine and silky, longi- 

 tudinal, parallel stria?. This tapers forwards, and widens backward towards the 

 root of the postero-ventral spine. A remnant of this striated rim is visible on 

 the other (left-hand) side of the carapace, passing from beneath the fringed edge 

 up to the anterior border, where the stria? of the fringe are closer together and 

 pressed nearly parallel with the edge. 



An intumed part of the ventral margin has been seen in a fragment to consist 

 of a finely reticulated band (about 5 mm. broad), tapering backwards and 

 bordered by a narrow, but thick, striated rim. 



This reticulated band and its rim were once a part of the outside of the test, 

 but turned down at an angle. As now seen from underneath, they lie compressed 

 on the inside of the fringe and a narrow smooth band, PI. XXVII, figs. 2 a — c. 



In PI. XXIV, fig. 1, there is also the relic of an abdominal segment, marked 

 with deep sinuous transverse lines, due to the overlapping flakes of the test. In 

 the ' Geol. Mag.,' vol. x, p. 485, pi. xv, fig. 3, the remains of three abdominal 

 segments are indicated, but they have been partly broken away since 1873. 



From black, non-calcareous shale above the Calderwood Cement-stone, Lower 

 Carboniferous Limestone Group, East Kilbride. At the Kirktonholm Cement 

 Works, East Kilbride. The counterpart of this remarkably fine specimen is in the 

 Museum of Practical Geology, London. It bears the original mark of the Geol. 

 Surv. Scotl., " n 3096 a," and the following label : — " Lower Carboniferous Lime- 

 stone Group. Shales above Calder Wood Cement-stone, Kirkstone Holme Cement 

 Works, East Kilbride, Lanarkshire. Cast of Dithijrocaris tricomis, Scouler." It 

 is this specimen that exhibited a portion of the outer part of the ventral border, 

 infolded and pressed flat. In hard black non-calcareous shale, PI. XXVII, 

 figs. 2 a, b, c. 



PI. XXIV, fig. 6. Mus. Techn. Coll. Glasgow. This is the original of 

 Dr. Scouler's fig. 2, p. 137, 'Records,' &c, 1835. 



Size. — Length of carapace (including spikes) 80 mm., breadth of carapace 

 36 mm., abdominal segments 28 mm. long, 12 mm. broad, longest spine 42 mm. 

 long, middle spine 25 mm. long, lowest spine 28 mm., not quite perfect. 



The two valves or moieties of an oblong carapace, folded together, and some- 

 what damaged by crush. They lie almost symmetrically, but by a transposition of 

 parts usual in decayed and floating Phyllopods, the three rather obscure abdominal 



