240 
PALjEONTOLOGY of new-york. 
Genus ACIDASPIS (Murchison). 
ODONTOPLEURA ( Emmhich). 
I prefer to adopt the name of Murchison, which is well understood in its application 
to a species in the central or higher Silurian strata of New-York. It is not easy to determine 
whether the name of Murchison or Emmrich has priority in regard to time; the works of 
the former, and the dissertation of the latter, bearing the same date. 
Dr. Loven ( Ofv. Vet. Acad. Sci. Stockholm , 1845) has attempted to show the identity of 
Acidaspis, Odontopleura and Ceraurus ; but the latter genus is quite distinct, as I shall 
show in the succeeding pages. 
299. 1. ACIDASPIS TRENTONENSIS. 
Pl. LXIV. Figs. 4 a, b t c, d, e,f. 
Compare Ceraurus crosotus , Locke in Am. Jour. Science, 1843, Vol. xliv, no. 2, p. 346. 
Odontopleura ovata, Emmrich, Dissertation, 1S39. 
— bispinosa, Id. SCient. Memoirs, 1845, Vol. iv, part 14, pag. 275, pl. 4, fig. 12. 
Cephalic shield subcrescent-form, broadly rounded and dentated in front, produced into 
elongated spines at the posterior angle, the connate segment at the base distinct; glabella 
of nearly equal width, somewhat straight, and having a projecting spine at the posterior 
margin, and two distinct rounded lobes or tubercles on each side, or in the furrow between 
the glabella and cheeks, being nearly disconnected with the former; cheeks with a lon¬ 
gitudinal or slightly oblique groove from the inner posterior base of the eye, extending 
forward, and a ridge from the front of the eye, extending forward and inward along the 
facial suture ; outer margin of the maxillae timbriated ; eyes round smooth tubercles ; 
body ten-jointed ; lateral lobes with a row of small tubercles on the anterior edge of each 
articulation ; caudal shield two-jointed, with a spinous margin. 
In our specimen, both the spines from the angles of the buckler, and the one from the 
posterior part of the glabella, are broken off. That they existed in accordance with other 
species of the genus, is clear from the appearance of the remaining portion. The extremities 
of the pleura, or lateral articulations, are prolonged into short spines as in the Odontopleura 
bispinosa of Emmrich cited above, and in the figure of the same species given by Bur- 
meister ; but the character of the caudal extremity, and the serratures on the margin of 
the buckler, as well as the tubercles of the middle lobe of the thorax, as represented by 
these authors, are different from our specimen. The form of the buckler, the tubercles of 
the glabella, eyes, etc., clearly point to Acidaspis of Murchison. We have another ana¬ 
logous species in the Delthyris shaly limestone, which resembles the Acidaspis brightii of 
England. 
