130 THE VOYAGE OF H.M.S. CHALLENGER. 



latter of which only the iliac origin (adductor longus) is present ; the absence of an 

 accessory semi-tendinosus, and the union of the inner head of the gastrocnemius with 

 the adductor (adductor magnus), two characters which we find in the Raptores ; the 

 exceptional presence of an abdominal origin of the rectus internus (semi-membranosus) ; 

 the great development of the soleus (anterior head of gastrocnemius), which, however, 

 only possesses one of the two tibial origins which we find in the Grebes ; the strength of the 

 tibialis posticus (plantaris) ; the entomyic type (type entomyen) of the deep portion of the 

 superficial flexor, its arrangement resembling that which is seen in the Grebe and certain of 

 the lamellirostral palmipedes (Swan, Goose, and Duck) ; the delicacy of the flexor tendon 

 of the hallux, not connected directly with the long femoral head, but lost in the fibrous 

 sheath of the latter ; the small size of the short muscles of the hallux ; the absence of 

 short muscles belonging to the second and third toes ; the non-division of the tendon of 

 the tibialis anticus ; the sub-division of the tendon of the peroneus longus into three 

 parts, one of which is attached to the base of the outermost toe." 



Muscles of Mastication. 



1. Digastric muscle. 



Der MundiJffner, Merrem. 



Le Crotaphite, Vicq d'Azyr, 1773, p. 584, No. L 



Dev Sehnaheloffner, Wiedemann, p. 74. 



Der pyramidcnformige Schnabcluffner, Tiedemann, p. 38.3, No. 1. 



Digastrique (part of), Cuvier, voL iii. p. 69. 



L'abaisseur de la mdchoire inferieure, Meckel, vol. viii. p. 162. 



L'abalsseur de la mdchoire inferieure, Gervais and Alix, p. 19. 



Attachments. — This muscle consists of two portions, a superficial and a deep. The 

 superficial portion is oval in form, and arises from the great transverse occipital crest, 

 the origin extending from the upper extremity of the latter downwards as far as the base 

 of a nipple-shaped projection of the temporal bone, which is situated immediately behind 

 the articulation of the occipital bone with the os quadratum, with which projection the 

 transverse ridge is continuous. The deep portion ai-ises from the outer surface of the 

 nipple-shaped process above referred to, as well as from that of the horizontal ridge with 

 which it is continuous in front. The fibres of both heads unite to form a single muscle 

 which is inserted into the posterior extremity of the ramus of the lower jaw. 



Action. — This muscle acting upon the posterior extremity of the lower jaw behind 

 the articulation of the latter with the quadrate bone, depresses that bone in front of the 

 articulation and opens the mouth. 



Relations. — The digastric lies behind the external auditory meatus. It is concealed by 

 the anterior fibres of the cervical cutaneous muscle, and rests against the side of the skull. 



