66 LINDSTRÖM, VISUAL ORGANS OF THE TRILOB1TES. 



Phacops (Acaste) quadriliueata Angelin. 



Pl. V figs. 37, 38. 



We ha ve not succeeded in finding any well preserved hypostom;i. 



The lenses of the cephalic eyes resemble uiuch those of the preceding species though 

 more elongate and ovate. Thev are covered by a membrane which surrounds their upper 

 moiety and between the lenses joins the interstitial test. In the horizontal section these 

 membranes surround the lenses as an annular wall. 





Phaetonides B 



A KIL 



Ph. Stokesi Murch. 

 pi. vi fig. n. 



The hypostoma somewhat reminds of that of Calyminene, has projecting angles and 

 a prominent knob below the straight anterior börder. The two oblique and oblong ma- 

 eulae are tubercular and plaeed near the lateral borders. This hypostoma is upon the 

 whole much related to that of Phillipsia and Proetus. 



Phillipsia Portlock. 



De Koninck figured a hypostoma of Phillipsia in his »Description des Animaux 

 Foss. de Belgique» as Cyelus Brongniartianus pl. LII fig. D and Novåk in III figs. 6, 7 

 copied it and corrected the error. It is provided with two glolmlar macuhe united by a 

 curved ridge. 



Phillipsia Eichwaldi Woodw. Novak III tig. 5 a hypostoma with globular maeuhe. 



We have been able to examine three different, unnamed or undetcrminated species, 

 which we distinguish by numbering them. 



Phill. No. / from the Keokuk group of Crawfordsville, N. America. The hypo- 

 stoma is broader than in the other species. The nearly horizontal elongated maeulae placed 

 near the median line, close to the lateral margins. 



Phill. No. 2 (pl. VI, figs. 15 — 18) probably from the Carboniferous formation of 

 Belgium is of a lengthened form. The elliptic macuhv in the groove, below the central 

 elevation. They are smooth and surroundéd by a Hat horder. 



r fhe cephalic eyes are much destroyed, but seem to have consisted of somewhat 

 semi-prismatic lenses or prisms of the same type as Dysplanus. 



Phillipsia Xk. -V (pl. VI tigs. 12 — 14) from the Carboniferous strat.a of Beeren Ei- 

 land communicated by Ilr 4. (i. Andersson. It comes near the preceding, is lengthened, 

 but hus broader and shorter anterior wings and the interiör surface just above the ]>os- 

 terior börder peculiarly pitted. The maeulae lying above this pitted field are ovate. The 

 lenses of the cephalic eye are foemisphaeric on the surface. 



