KONGL. SV. VET. AKADEMIENS HANDLINGAH. BAND 34. \:o 8. 65 



Phacops Emmrich. 



Maculae figured of Phac. (Acaste) Downingiae. Salter Monogr. pl. 2 fig. 34b, p. 25 

 »high u|> <>ii each side a small tubercle . 



Phac. råna Hall Pal. N. Y. vol. VII, pl. VIIIa, fig. is. Hypostoma vvith the Large 

 commalike maculae high up. 



Of the following species Ph. cephalotes and Ph. macrophthalmus belong to the 

 genus Phacops proper, while Phac. quadrilineata, as well as Ph. Downingiae are of a quite 

 different generic type. The name Acaste proposed for thern is uot good as Leacb in 

 1817 named a Cirrhiped as Acasta. 



Ph, cephalotes Barr. 



Pl. V tigs. 35, 3G. 



The hypostoma is elongate, almost triangulär, tricuspidate a1 the posterior börder, 

 a little above this there is a crescentshaped ridge, and still a little higher above this and 

 the median horizontal line, the two macula? as diminutive tubercles. Seen with magni- 

 fying powers they are slightly oblong ur remform. 



Ph. macrophthalmus Burm. 



Pl. VI tigs. 1—9. 



The triangulär hypostoma has a little below the median horizontal diameter two 

 shallow grooves, and a little above the same diameter the extraordinary minute maculae 

 may with some care be observed, tigs. 8, 9. They are visible as a small hare, smooth 

 spöt amongst the curious elevated and incoherent terrace lines of the surface. The ex- 

 ceedingly small size of these maculae naturally does not allow any research of their struc- 

 ture. They are rather in this species and many of the congeneric to be regarded as 

 small ocelli. In some specimens these spöts are quite rudimentary and are reduced to the 

 smallest area possible. The anterior wings are of a peeuliar earlike shape, finely striate, 

 enlarged and Hat near the hypostoma and ending in a little hollow horn (tigs. 6, 7). 

 A little below it, the posterior win t <>- einerges as a small angular knob. The aggregate 

 cephalie eyes are more distinct. 



As the vertical section learn us the regular ovate lenses consist generally of clear, 

 crystalline calcareous spar and are on the surface covered by an extremely thin mem- 

 brane, not a common one for all, but a separate cornea for each lens, which envelopcs 

 its superior moiety and continues down as a thickened appendix between the lens and 

 the interstitial test (figs. 3 — ö). In the horizontal sections it surrounds the lense> as an 

 annular wall. Around some lenscs there is as if still another ring lay outside this, but 

 more indistinct, probably only clearer portions of the test surrounding them. The checks 

 close to the lenses are indistinctly perforated by longitudinal tubi - 



