520 WALTER EDWARD COLLINGE. 
ix. THE CRANIAL AND OTHER BONES. 
But a very brief reference is necessary to the cranial and 
other bones of Acipenser. The nomenclature used is mainly 
that of Parker (58). 
The post-temporals (Pl. 40, fig. 13, p. ¢.) are two large 
dermal scutes lying at either side of the head, posterior and 
lateral to the dermo-occipital. They are bounded in front by 
the epiotics and conduct the main canal. 
Epiotics (Pl. 40, fig. 13, ep.).—T wo irregular scutes having 
a lateral position to the dermo-occipitals. They form the lateral 
posterior border of the parietals and the posterior border of 
the squamosals. In their anterior portion the occipital com- 
missure passes off from the main canal. 
Squamosals (Pl. 40, fig. 13, sg.).—T wo large scutes form- 
ing the lateral borders of the parietals. In their anterior 
portion the main canal divides into the supra- and sub-orbital. 
The dermo-ect-ethmoids (= the prefrontals of many 
authors; Pl. 40, fig. 12, d. ec. eth.) lie in front of the squamosals. 
Ventrally they are bounded by the first of the circum-orbital 
series ; anteriorly they form the dorsal boundary of the orbit, 
extending as far as the nasal capsules. The chain of canal 
bones conducting the sub-orbital branch passes over the poste- 
rior portion of either side. 
Dermo-occipital (Pl. 40, fig. 18, d. oc.),—A median some- 
what dagger-shaped scute forming the posterior border of the 
parietals; the most anterior portion passes between the parietals 
for some distance and is overlapped by them. It is traversed 
by the occipital commissure. 
The parietals (Pl. 40, fig. 12, pa.) are two large median 
scutes bounded posteriorly by the dermo-occipital and epiotics, 
laterally by the squamosals, and anteriorly by the frontals and 
dermo-ethmoid. In very large specimens which I have 
examined the occipital commissure passes through the poste- 
rior portion of the parietals as well as the epiotics and the 
dermo-occipital scute. 
The frontals (Pl. 40, fig. 12, fr.) lie at either side of the 
