4KT. 15 ANATOMY OF THE EARED AND EARLESS SEALS — HOWELL 135 



process. The ossification of the border of the auditory meatus is 

 regular and uninterrupted in fetuses ^ and the occipital condyles are 

 usually narrow. The vertebral spines of the anterior thorax are well 

 developed. The scapula is subtriangular (never falciform) and with 

 a distinct acromial process. The greater tuberosity of the humerus 

 is higher than the lesser and there is no entepicondylar foramen. 

 The ilium is but slightly curved — not markedly and abruptly bent 

 lateraJ. The femur has a lesser trochanter. 



There is no external ear. Neither fore nor hind feet are used 

 as primary aids in terrestrial locomotion. The area of the forefeet 

 is reduced and the axilla falls opposite the wrist. The external 

 surface of the hind feet is increased, relative to the length of the 

 leg, these being plainly indicated as the chief means of aquatic 

 propulsion rather than the forefeet. The astragalus has a posterior 

 extension as long as that of the calcaneum, and the foot is prevented 

 from assuming a plantigrade posture by the unusual tension of 

 the flexor hallucis longus muscle. There are no cartilaginous 

 prolongations of the digits, and the palms and soles are usually well 

 haired. The nails are well formed and never vestigeal. The testes 

 are abdominal in the adult male. The tooth formula is : 



1 or 2 1 ^ 4 0, 1 or 2' 



total 26 to 38. The canines are rather poorly to moderately de- 

 veloped. The skull has no postorbital process, and there is no alis- 

 phenoid canal. The mastoid is relatively inflated and the mastoid 

 process either poorly defined or else not continuous with the paroc- 

 cipital process. The ossification of the border of the auditory meatus 

 is irregular and interrupted in the fetal state ® and the occipital 

 condyles are usually broad. The vertebral spines of the anterior 

 thorax are vei'y poorly developed. The scapula is often somewhat 

 falciform and the acromial process is not well marked. The lesser 

 tuberosity of the humerus is usually higher than the greater, and 

 there is often present an entepicondylar foramen. The ilium is 

 markedly and abruptly bent laterad. There is no femoral lesser 

 trochanter. 



Many other characters of differentiation exist, but for the most 

 part these are slight and not so well suited for purposes of diag- 

 nosis. In addition, a few of the above characters need verification 



' In the Otarlidae this was determined for Callorhinus only, but it is probably a uniform 

 character. 



• Determined in the case of Phoca vituHna only. 



