Cope.] 48 [May 4, 
ing the line drawn vertically from the base of the ventral fin. The pos- 
terior extremity of the base of the second dorsal stands above the begin- 
ning of the last third of the base of the anal. The proximal portion of 
the inferior limb of the caudal fin, is very little prominent. The teeth are 
transverse and present only a low transverse median keel. 
Uniform leaden brown above ; below light yellowish brown. 
M. 
MotalslenathPpmanccoss o- cee ce SOs US tod DudouueS 3808 
Length to bases of superior teeth............. 30 1a0h006 .026 
Ho SMe ECLOMA MMS A ciye fy ob -letarenersekorncte crake erate 072 
oe “o> Svieriral sins. om eters Biro ereeiicie eietershe 143 
se EE sb QING FUN Shes ce dfay ont ototer reset sees pe ereneerers .202 
Width between upper lips at angle of mouth........... .019 
From the Pacific Ocean at Pacasmayo, Peru. 
This shark differs from the species described by Giinther in the relatively 
long muzzle and narrow arcade of the mouth, excepting in the case of the 
M. manayo Schieg., which differs from the Jf mento in the more poste- 
rior position of the dorsal fin. Prof. Gill has described two species from 
the Pacific Ocean, the W. californicus and M. dorsalis.* The former differs 
from the present one in the more posterior position of the ventral fins 
which are considerably behind the posterior angle of the dorsal, and the 
muzzle is shorter. In the WZ. dorsalis from Panama the dorsal fin is, ac- 
cording to Prof. Gill, more posterior in position, since only one-fourth of 
its base stands above the pectoral; in MW. mento, three-fourths of the base 
of the dorsal stands above the ventral fin. 
45. PSAMMOBATIS BREVICAUDATUS, Sp- nov. 
Anterior borders of the disc broadly rounded, consisting of the anterior 
portions of the pectoral fins, the only indication of the snout being a small 
tubercle below the median point. Disc broader than long, subrhombic, the 
lateral margins broadly rounded. Posterior border of pectoral fin overlap- 
ping the anterior part of the ventral. Ventral fins with the border not 
very deeply emarginate. Tail only one-fifth longer than the claspers, with 
broad lateral fold, two superior, and a rudimental terminal fin. Nasal fis- 
sures with two lamine, which are not united with each other nor with 
those of the opposite side. The posterior or internal is anteroposterior, the 
anterior or external, is rolled into a tube. 
The distance between the outer margins of the nostrils is equal to that 
between each one and the extremity of the snout, and one-half greater than 
that between each and the nearest part of the margin of the disc. The in- 
terorbital space is little concave, and is wide, exceeding the combined 
length of the orbit and spiracle. The upper surface of the head, and a 
broad band on both surfaces of the anterior part of the disc are covered 
with minute spinules. The other surfaces are smooth, with the follow- 
ing exceptions. Two spines anterior to the orbit above ; a spine near the 
* Proceedings Academy, Phila., 1864, p. 148-9. 
