PROETUS. 57 



four to thirteen in species found in Bohemia) ; the pleura do not extend to the 

 margin of the pygidium, which is often smooth. 



The surface of the test is most frequently smooth or finely granulated ; in a 

 few species it is striated; and rarely it presents a combination of both kinds of 

 ornamentation. 



Mr. J. W. Salter, in his " Palseontological Appendix " to the ' Memoirs of the 

 Geological Survey,' 1858, vol. ii, part i, p. 337, writes as follows concerning the 

 generic characters of Proetus : 



" A very usual character of this genus is the possession of a strong tubercle, 

 terminating the neck-segment on each side, and nearly separating it. Burmeister, 

 however, in his second edition, has considered the species having this thickening 

 and the obscure glabella furrows more strongly marked as forming a distinct 

 genus, which he calls Monia. M'Coy had anticipated him by a few months in the 

 name of Forbesia without referring to Proetus. We prefer, with Loven, to 

 consider both as belonging to one genus. 



" The glabella shows two or three lateral furrows, but is sometimes quite smooth. 

 Body-rings ten. The tail has but few lateral furrows, seldom more than seven or 

 eight, and in this, as well as in the additional body-segment, the Silurian genus 

 differs from the Carboniferous Phillipsia and Griffithides, which are else very 

 nearly related to it." 



27. Peoetus? levis, H. Woodw., 1883. 1 (See Woodcut, fig. 1.) 



Phillipsia Beongniaeti ?, Baily. Mem. G-eol. Surv. Ireland, Expl. Mem. Sheets 



102 and 112, 2nd edit., p. 19, 1875. 

 Peoetus ? levis, H. Woodw. Geol. Mag., Decade ii, vol. x, p. 4t4t&, and woodcut, 

 1883. 

 Cephalothorax unknown. 



Pygidium — 22 mm. broad and 16 mm. long; smooth, 

 semicircular, one fourth broader than long ; axis convex, 

 7 mm. wide, one third the breadth of the pygidium 

 at its anterior border, smooth, moderately elevated ; 

 axal furrows broad; where decorticated showing evi- 

 dence of the coalescence of about twelve somites or 

 rings 12 mm. long; tapering to a blunt extremity, fig. l. Pygidium of iv<w« 



levis, H. Woodw. 



Mo- 



which does not reach to the posterior margin, but carboniferous ' Limestone, 

 leaves a smooth border 4 mm. wide behind it; pleurae Sftwic^atSS^e. **"* 

 slightly convex, very indistinctly furrowed; margin 



1 The existence of this specimen was not known until too late for insertion in the earlier pages of 

 this Monograph. It should naturally be placed as the first genus instead of the fourth in our series. 



