88 BRITISH PALAEOZOIC PHYLLOCARIDA. 



selected outlines drawn from the slab in 1890, we see the rounded front in figs. 3, 

 4, 5, 9, 11, 15, 17 of the Report, and partially in figs. 7, 10, and 14 of that 

 Report. Figs. 3 and 15 (1890) retain some of the proportionate height of 

 PI. XIV, fig. 8 ; but others seem to have become narrower by cross-pressure, but 

 this may have been an original specific feature (although very doubtful). Some 

 trace of the hinder ogee outline is visible in figs. 3, 5, 7, 9, 11, and 15 of the 

 Report (sometimes neater than in PI. XIV, fig. 8) ; also in figs. 14 and 17, which 

 are apparently reversed valves, with the dorsal edge downwards. The superficial 

 longitudinal lines are evident in all the valves ; and 4, 5, 7, and 15 (1890) show the 

 backward branching, but in fig. 1 7 the bi'anching veins seem to have a forward 

 direction. Unequal pressure may have modified these appearances. We regard 

 these smaller valves as being most probably immature forms, rather than showing 

 either sexual or specific differences. Abdominal segments are attached to the 

 valves in figs. 3, 4, 7, and 14 of the Report; and are separate in figs. 6, 8, 12, 

 13, and 16 of that series. In shape, size, and ornament these differ too much for 

 us to pretend to decide whether they are really all of one kind or not, the modes 

 and degrees of preservation probably making more distinctions than originally 

 existed. PI. XIV, fig. 8, represents fig. 1 of the Report, and fig. 9 comprises 

 figs. 9, 10, 11 of. the Report. 



Bearing in mind the gregarious habits of modern Bntomostraca, it seems most 

 probable that we have here another illustration of the crowding together of 

 numbers of individuals of one species which lived in the same shallow lagoon, a 

 portion of which may have been dried up (as in a modern shore pool), leaving its 

 inhabitants to perish in the sun and to be covered up with a fresh layer of mud 

 by the next tide. Such a local accumulation of animal matter may have caused 

 a segregation of special mineral matter in the matrix, and have given rise to the 

 local concretion. 



The slab and its counterpart from the Arenig slates, as mentioned above 

 (p. 86), collected by Professor T. M'Kenny Hughes, are preserved in the 

 Woodwardian Museum at Cambridge. 



A small specimen of an imperfect valve in the Woodwardian Museum (marked 

 yfo) from Wern, near Portmadoc, in a bluish schistose mudstone, weathering 

 greenish-grey, shows a definitely sinuous (ogee) posterior margin, thus presenting 

 a feature seen in some specimens of Saccocaris minor (as also in Ceratiocaris). 

 This posterior moiety of a valve is 23 mm. long by 15 mm. high. We figure it 

 here (PI. XIV, fig. 10) as being probably of the same genus, if not of the same 

 species as 8. minor. 



This specimen was described at p. 220 of the First Report (1883), and 

 figured in outline at p. 179 of the Sixth (1888) Report, fig. 10, as being doubtfully 

 a part of the valve of a Ceratiocaris, 



