MARYLAXD GEOLOGICAL SURVEY 47 



gingival foramina, five in number in the specimen, are placed below 

 the npper margin internally, are abont one line in diameter, and 

 open very obliquely forward into grooves almost horizontal, from half 

 an inch to one inch long. The labial foramina, of which there are the 

 remains of seven in the specimen, are about half an inch external to 

 the upper margin, about two lines in diameter, and open very obliquely 

 forward. 



Vertical diameter 3 inches [75 mm.] 



Transverse diameter 2 inches [50 mm.]" 



In 1869 Cope described EscJirichtius prisons as intermediate in size 

 between E. cephalus and E. hptocentrus and E. expansus and E. pusillus. 



Occurrence.— Caj^yert Formation. Charles county near the Patux- 

 ent river. (Fide Cope.) 



Collection. — Philadelphia Academy of Natural Sciences. 



SiPHONOCETUS CLARKIANUS Cope. 



Plate XXV, Fig. 4. 



Siphonocetus clarklanus Cope, 1895, Proc. Amer. Pbilos. Soc, vol. xxxiv, p. 140 

 pi. vi, fig. 4. 



Description.— De&cr\\)Q(\. from fragment of mandibular rami. "The 

 cranium of this genus is unknown, but it is probably similar in char- 

 acter to that of the Cetotherium of Brandt. This genus differs from 

 Balgenoptera in having the elements between the supraoccipital and the 

 nasals much elongated, so that there is a sagittal crest of greater or 

 less length, and in the non-union of the dia- and parapophyses into a 

 vertebral canal,' in which it agrees with Eschrichtius of Gray. Some 

 of the rami described belong possibly to species of Balgenoptera, and it 

 remains for future discoveries to ascertain which these are 



" In dimensions it .... is only exceeded by ... . Cetotherium lep- 

 tooentrum and C. cephalus. It compares more closely in dimensions with 

 the C. pohjporum from the Chesapeake group of North Carolina. From 



1 See American Naturalist, vol. xxiv, 1890, p. 611, where these genera are charac- 

 terized : but Van Beneden's name, Plesiocetus, is used for Cetotherium, and the latter 

 name for Eschrichtius of Gray. 



