NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 83 



APHELASPIS CAMIRO (Walcott) 



Plate 12, figures 1-17 



Crepicephahis cmniro Walcott (part), 1916a, p. 205, pi. 32, figs. 2, 2'. 

 Uncaspis camiro (Walcott) Kobayashi, 1935, p. 279. 

 Aphelaspis camiro (Walcott) Resser, 1938a, p. 60, pi. 13, fig. 27. 



Available material. — Resser properly restricted the name to Wal- 

 cott's holotype cranidium, excluding the pygidium which not only does 

 not belong to the species, but probably is a trilobite of the Crepiceph- 

 alus zone. The hypodigm includes a number of paratype cranidia well 

 preserved in limestone. The species was collected at other localities 

 by Dr. Oder and the author. From these collections the proper free 

 cheek and pygidium could be identified unequivocally. Many of these 

 pygidia were then discovered in the collection from the type locality 

 in the U.S. National Museum. 



Description. — Glabella somewhat smaller in proportion to the cra- 

 nidium than in other species of the genus. Occipital ring bearing a 

 small node near the posterior margin. Frontal area unusually long, 

 averaging 0.8 times the glabellar length ; as in other species, however, 

 this ratio varies considerably among the individuals from one bed. 

 Anterior sections of facial sutures diverging at average angle, making 

 the cranidium very wide between the anterior angles. Border furrow 

 better impressed than usual in the genus. Border slightly convex, its 

 sagittal length averaging two-thirds the length of preglabellar field; 

 border furrow showing in most, but not all, specimens a definite 

 median inbend, and generally pitted on the outer surface. Preglabellar 

 field as a whole rather flat, showing a low median boss. Palpebral area 

 upsloping, about half the glabellar width. Ocular ridges transverse 

 to slightly slanted backward. Palpebral lobe averaging 0.3 times the 

 glabellar length, and about 0.5 times the distance from posterior end 

 of palpebral lobe to posterior margin. Posterior area at least as wide 

 (tr). as occipital ring. Length of largest observed cranidium 22 mm. 



Free cheek with distinct, flat border set ofif by definite furrow, 

 deeper in anterior portion, and long, slowly tapered genal spine, flat 

 on the upper side. 



Pygidium on average 1.75 times as wide as long, with a somewhat 

 pointed shape. Axis relatively large, prominent, tapered, rounded pos- 

 teriorly, showing 3 very distinct rings plus a terminal section. Anterior 

 outline of pleural lobes after a short transverse course turning back- 

 ward like the first pair of pleural furrows. Two other pairs of furrows 

 may be faintly indicated. Border furrow and border poorly defined. 

 Length of largest pygidium 3.8 mm., width 6.8 mm. 



Discussion. — This is one of the most distinctive species of Aphe- 

 laspis. Larger cranidia may be distinguished by the long frontal area. 



