142 TRANSACTIONS OF THE [MaR. 17, 
the eyelobes are opposite the posterior two-thirds of the glabella, 
narrow and moderately arched. Dorsal suture, except at the 
eyelobe, nearly parallel to the side of the elabella. 
Sculpture. This consists of tubercles which on some parts of 
the shield are arranged in sub-parallel rows (e. g., the back of the 
glabella and the front of the fixed cheeks). 
Size. Length of the head shield 21 mm.; width between the 
dorsal sutures, at the front 21 mm.; at the eyelobes 26 mm. 
Horizon and locality. In the purple-streaked Sp ast of 
Assise 3, Hanford Brook. Scarce. 
This species is named for the discoverer, W. D. Machen? 
Micmacca VAN-INGENI n. sp. Pl. xi., figs. 1 a and D. 
This species differs from the preceding in the following re- 
spects ; the glabella is more prominent and narrower and has 
deeper furrows, and the occipital furrow is also more distinct. 
The occipital ring bears a strong spine, projecting upward and 
backward; the width of the spine and ring together is equal to 
that of the fixed cheek. 
Detached pleura which have a prominent spine on the poste- 
rior ridge of the ring, probably belong to this species. 
Sculpture. This consists of distinct granulations covering 
the whole surface of the test. 
Size. Length from the front of the glabella to the tip of the 
occipital spine 20 mm.; width between the eyelobes 22 mm. 
Horizon and locality. Sandstones of Assise 3, at Hanford 
Brook. Scarce. 
Named for the collector, Mr. Gilbert van Ingen. 
This species is allied to Zacanthoides spinosus Wale., of the 
Eureka district in Nevada,* by the form and size of the glabella, 
and the large occipital spine; it however has wider fixed cheeks, 
and no trace of the long posterior extension of the dorsal suture, 
necessary to a Zacanthoides. Z. sptnosus is stated to have a 
wide range, even up into the Potsdam horizon (Upper Cam- 
brian) ; the lower horizon is not much above the Olenellus Zone; 
possibly there are two species, of which only the later one has 
the extended posterior suture; the earlier one only is shown to 
have the heavy occipital spine. 
MIcMACCA RECURVA 0. Sp., Pl. x., figs. 3 a to c. 
Form of the head shield semi-circular. Anterior margin with 
a narrow, upturned rim. Glabella quadrate, rounded in front, 
slightly wider opposite the eyelobes than elsewhere, faintly im- 
* U.S. Geol. Sury. Bul., 30, p. 184, pl. xxv. figs. 6 and 6 a. 
