ART. 19 A MIOCENE PORPOISE FROM MARYLAND — KELLOGG 45 



The three anterior caudals of this fossil porpoise do not have their 

 transverse processes pierced at the base by a foramen. In Sotalia 

 the first and second caudals have transverse processes without per- 

 forations and on those near the middle of the series the dorsal orifice 

 of the lateral vertebrarterial canal is nearer to the posterior epiphysis 

 than in pernix. 



On the anterior caudals the neural canals are narrow and high and 

 they progressively decrease in height up to the fourteenth, beyond 

 which they disappear entirely. The neural arches increase in diam- 

 eter anteroposteriorly from the first to the fourteenth and on the last- 

 mentioned caudal extend nearly the full length of the centrum. In 

 correlation with the progressive shortening of the neural arches 

 toward the end of the series the metapophyses drop down to a lower 

 level on each succeeding vertebra, those on the first caudal being ele- 

 vated at least 30 mm. above the top of the centrum, while those on the 

 fourteenth are not more than 3.5 mm. above the centrum. The trans- 

 verse processes decrease in size from the first to the eleventh and are 

 vestigial on the twelfth. On four of the caudals near the middle of 

 the series (11th to 14th) there are a pair of longitudinal platelike de- 

 scending processes upon the extremities of which are situated the 

 facets for the chevron bones. 



First caudal. — All of this caudal (pi. 11, fig. 3) is well preserved 

 save for the distal portion of the neural spine. The centrum (pi. 10, 

 fig. 2) is approximately equal in length to the last lumbar and is 

 constricted behind the neural arches, with two small articular facets 

 on the ventral surface at the posterior end for the corresponding 

 chevron. The metapophyses are damaged, but their superior mar- 

 gins were originally at least 30 mm. above the top of the centrum. 

 The neural arches are inclined forward, the minimum anteropos- 

 terior diameter being less than one-half the length of the centrum. 

 The neural canal is narrow and both neural arches are cracked near 

 the middle. The epiphyses are thin. The transverse processes are 

 short, constricted anteroposteriorly near the base and expanded at 

 their distal extremities. The posteroexternal angles are quite 

 prominent. 



Second caudal. — The entire neural spine, both metapophyses, the 

 major portion of the neural arches, the anterior epiphysis, and the ex- 

 tremity of the right transverse process are missing. The centrum 

 (pi. 10, fig. 3) is approximately equal in length to that of ih^ first 

 caudal. The transverse processes (pi. 11, fig. 4) are shorter than 

 those on the preceding caudal, more expanded anteroposteriorly at 

 the extremity, and the posteroexternal angle is prolonged backward. 

 The paired facets for the chevron on the inferior surface of the cen- 

 trum at tlie posterior end are relatively large. The neural canal is 

 not more than 13 mm. in height posteriorly. 



