80 BULLETIN UNITED STATES GEOLOGICAL SURVEY. IVol.Yl. 



The symphysis mandibuli is short. The rami are wide, and are ilat 

 below, the inferior surface forming a rounded right angle with the in- 

 terior surface. The angular process is in line with the external border 

 of the ramus. 



The sculj)ture of the cranium proper is strong, consisting of pits sepa-- 

 rated by strong, narrow ridges, forming a honeycomb pattern. The 

 fossse are smaller on the buccal regions. On the anterior part of the 

 mandible the fosspe are distinct ; on the median and posterior part the 

 ridges become linear. A narrow triangular space on the external side 

 posteriorly, with its long apex on the inferior margin, is smooth. 



There are two subequal obtuse teeth, on the border of each premaxil- 

 lary bone. I cannot count the number on the maxillary, but there are" 

 four anterior to the line of the anterior border of the orbit. Of these 

 the next to the anterior one is larger than the rest, though of the same 

 shortly-conic, obtuse form. These teeth are rather large for the size of 

 the skull. At a point near the middle of the ramus of the mandible,, 

 where it is broken off, there may be counted five teeth in a transverse 

 series. Of these the second from the external border is the largest, and 

 has a regularly rounded crown. Six teeth may be counted on a trans- 

 verse fracture of the palatine bone. Of these the four external have 

 obtusely rounded crowns, and the third from the external border is the 

 largest. The crowns of all the teeth are hollow. 



■ Measurements. 



M. 

 Length of cranium to transverse line connecting posterior borders of quadrates. .077 



Width between same points 082 



Length of axis of cranium to line connecting anterior borders of orbits 018 



Interorbital width O'M 



Longitudinal diameter of orbit 01& 



Length from orbit to nostril 01& 



Projection of miizzle beyond mandible 010 



Length of alveolar edge of premasillary 007 



Height of crown of large maxillary tooth - 0045 



Fore-and-aft diameter of maxillary 0O35 



Width of mandibular ramus below at middle 020 



This species considerably exceeds in size those referred by Dr. Fritsch 

 to Sparodus, as it was probably rather larger than the Frotonopsldes of 

 recent waters. Its physiognomy is peculiar, as the prominent muzale 

 and lateral orbits are unusual among Batrachia. 



DrMETRODON SEMIRADICATUS Sp. nov. 



A considerable part of the skull and some limb bones represent this 

 species. There are no vertebrae referable to the specimen, but the two 

 maxillary and premaxillary bones sujtport nearly all the teeth in an 

 excellent state of preservation. Continuity of the dental series is 

 preserved by one maxillary bone or the other, excepting just at the ex- 

 tremity, where there is a slight interruption on both sides. On one of 

 them it must be verj^ slight. 



