608 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii. 



occipital, exoccipital, and parasphenoid. The myodome is very large 

 at its mouth, but abruptly grows narrow a short distance back. It 

 does not open to the exterior posteriorly. The cranial cavity is 

 entirely closed anteriorly except in two places, one small hole through 

 the orbitosphenoid and one between the basisphenoid and alisphenoid. 

 The basisphenoid widens over the base of the auditory bulla. It 

 forms but little over a third of the occipital condvle. The supraoc- 

 cipital is but little covered h\ the parietals. It ends squarely at the 

 frontals, without dividing them at their ends. A strengthening ridge 

 runs upward on its crest from the base to the point. The parietals 

 are elongate and project anteriorly beyond the supraoccipital. Pos- 

 teriorly they cover the top of the epiotic to the articulation of the 

 post-temporal. The epiotics have no backward projecting process. 

 The surface over which the post-temporal lies is large and nearh' hori- 

 zontal. The opisthotic covers the suture between the exoccipital and 

 the pterotic below. It has a slight nodule developed, to which the 

 lower limb of the post-temporal is closely joined. The parasphenoid 

 is long and narrow. It sends basitemporal wings upward at the mouth 

 of the myodome, which join descending processes from the prootics, 

 inclosing behind a large lateral opening into the myodome. The para- 

 sphenoid grows broad over the floor of the myodome, and then abruptly 

 narrow, running backward in a depression in the basioccipital. It 

 ends in a point some distance from the end of that bone. The basi- 

 sphenoid sends a long, slender process down to the parasphenoid. 

 Anteriorly the basisphenoid extends partly around a hole into the 

 cranial cavity. The large alisphenoids meet broadly at the median 

 line. Posteriorlj^ they are notched b}- the hole between them and the 

 basisphenoid. The orbitosphenoids are large. They meet at an angle 

 and ankylose. There is a small hole at the median line opening into 

 the cranial cavit}'. The frontals project widel}' over the ethmoid to 

 opposite the front of the vomer. Anterior to the ethmoid they are 

 divided, leaving a large notch. The prefrontals are in contact behind, 

 but are separated in front by the ethmoid. The olfactory foramen 

 pierces them transversely across the cranium. There is an area of 

 cartilage between the ethmoid and the vomer. The nasals are large 

 and are attached to the ends of the projecting frontals. Thev nearly 

 touch each other in front and develop laterally around the end of the 

 snout, inclosing a chamber behind. 



FACE BONES. 



The opercle has a prominent ridge and two slight ones radiating 

 from a conmion center. Between each ridge its posterior edge is 

 concave. Its upper end extends above the head of the hyomandibular. 

 The subopercle is very thin and flexible, and onlv slight!}^ calcified. 

 The preopercle is deeply channeled and has two rough spines at the 



