068 MBSSKS. B. C. A. WINJ3LE AND r. G. PAHSONS ON [DeC. 17, 



out ; we have noticed, too, that the fibres of the more superficial 

 layer run forward and outward, while those of the deeper layer 

 ruu backward and outward. 



In the Ass (62), Steel points out that the muscle is often divided 

 anteriorly into two laminfe. 



In the Horse (56), Chauveau says that a delicate slip lies super- 

 ficial to the mylo-hyoid, but from the antero-posterior direction of 

 its fibres it probably represents a mento-hyal muscle. We have 

 some little doubt as to whether the sixperficial layer in the Rumi- 

 nants may not represent a mento-hyal muscle the fibres of which 

 have become deflected, but this is a mere speculation; and the 

 occasional presence of these two layers is probably a repetition of 

 the splitting tendency of the mylo-hyoid, ^hich formerly gave rise 

 to the anterior belly of the digastric. 



The nerve-supply is from the mylo-hyoid branch of the 

 fifth. 



Genio-hyoid and Oenio-hyoglossns. — These t\^'o muscles have the 

 usual mammalian attachments throughout tlie Order, except that in 

 the Equidse, where the glosso-hyal process of the hyoid bone is 

 very large, they are attached to it. In the Eed-Eiver Hog (11), 

 owing to the imperfect development of the mylo-hyoid already 

 alluded to, the genio-hyoid is seen before removing that muscle. 



In the Ass (62), Steel points out that the genio-hyoid sometimes 

 sends a distinct band to the genio-liyoglossus opposite the middle 

 of the intermaxillary space. 



In the Giraffe (31), Owen points out that both these muscles 

 rise by tendon. 



The nerve-supply was the hypoglossal in all the animals which 

 we dissected. 



Hyoglossus. — This is the hyoglossus brevis of many veterinary 

 surgeons, it rises from the basi- and thyro-hyals, and in the Equidae 

 from the glosso-hyal process as well ; the fibres run much more 

 forward than upward, and in some cases — e. ^. the Mouflon (45) 

 and Elephant (74, 75, 77)— the fibi-es coming from the basi-hyal are 

 quite distinct and have a somewhat more vertical direction than 

 those coming from the thyro-hyal. AVe wou^ld prefer to speak of 

 the fibres coming from the basi-hyal as the basi-glossus, but 

 Watson (XXX.) calls them hyoglossus anterior, and Miall and 

 Greenwood (XXIX.) hyoglossus minor, while Steel (XIX.) intro- 

 duces a novelty by speaking of them as hyoglossus brevis. In 

 Cuvier and Laurillard's plate (I.) the Elephant's basi-glossus is 

 larger than the rest of the hyoglossus, and in the Giraffe Joly and 

 Lavocat (XII.) say that the basi-glossus is the only part present. 

 In the Ass, Steel describes the basi-glossus as sometimes getting an 

 origin from the stylo-hyoid element, though this is not the normal 

 arrangement ; and Kinberg in the Chevrotain describes the " baseo- 

 glossus " as coming from the anterior part of the body and styloid 

 cornu (cerato-hyal). 



The nerve-supply seems always to be the hypoglossal. 



Masto-styloidens. — This muscle is apparently present in all 



