Cope.] J-4o [April 5, 



Measurements. m. 



Length anterior to parietals above 225 



Length of occipital from base of foramen magnum to apex 



(on curve) 290 



Width of occipital condyles and foramen 140 



The mandible of this species is unknown. The size is not far from that 

 of the Cetotherium pusillum and Siphonocetus expansus of Cope. Should 

 either of these turn out, on the discovery of the skull, to be Cetotheri- 

 form, it will become necessary to compare them with the present species. 

 The total length of the animal was about twenty or twenty- five feet. 



Cetotherium crassangulum, sp. nov. 



This species is represented by an imperfect skull, to which adhere three 

 cervical vertebrae, the posterior parts of both mandibular rami, parts of 

 the hyoid arch and a humerus. The sagittal part of the skull is crushed 

 and the frontal bones somewhat displaced outwards. Large portions of 

 the nasal bones remain, but the premaxillaries and maxillaries are mostly 

 wanting. By excavating at the proper point the right otic bulla was 

 brought to light. The presence of this structure, together with a consid- 

 erable part of the mandibular rami, enables me to compare the individual 

 with known species and to determine its specific reference with certainty. 

 The cobssification of all the epiphyses shows that the animal is adult. 



The species belongs to that group in the genus Cetotherium which is 

 characterized by the presence of a developed angle of the mandible, 

 but where it is short and broadly truncate. The angle is, however, 

 scarcely separated from the condyle, and partakes of the articular sur- 

 face, apparently much as in the Balmnoptera emarginata of Owen. 

 It is further distinguished from such species as G. priscum, G. meyerii and 

 G. klinderii by the oval and little-compressed form of the otic bulla, 

 resembling in this part rather the G. rathkei. From the G. megalophysum 

 the bulla diflFers by the much smaller dimensions as well as the different 

 form. Thus while the exoccipital width of the skull of the G. crassan- 

 gulum is half as great again as that of the G. megalophysum, the length of 

 the bulla is only about three-quarters that of the latter. The bulla of the 

 G. cephalus Cope is very diff"erent in form from that of either species. It 

 is of the compressed type and is a little smaller than that of the G. crass- 

 angulum. It is truncate both anteriorly and posteriorly, which is not the 

 case with that of the latter species. 



Although the sagittal crest is crushed away, it is evident that it is much 

 less elevated relatively to the width of the skull than in any of the species 

 so far known. This elevation, allowing for the injury, was about equal 

 to that in the G. megalopJiysum, measured from the floor of the foramen 

 magnum. The exoccipital width is one-half greater than that of the 

 latter species. The nareal orifice was about as far in advance of the 

 supraoccipital angle as in the G. megalopJiysum and much further than in 

 any existing whale. The supraorbital portions of the frontal are wanting 



