MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 157 



into the base of the depression running- back from the radular opening. Outside of this is 

 another flat muscle, the radular (R), having its origin just in front o the .ntermvl Ungual. It 

 runs forward and inward, and, uniting with its fellow on the opposite side, is attached to the 

 anterior side of the ascending portion of the radidar sac. Above the two muscles ]ust described 

 t a very much larger mu.^-i; which forms the bulk of the tongue. T., this have given 

 the name external Ihigual (EL). Its origin lies above the origins of the other two muscles 

 From this it runs forward and upward and inward, partly to join its fellow of the opposite side 

 in forraino- a sling which covers the whole of the ascending portion of the radular sac anteriorly , 

 "nd partlv to be inserted dorsally along the ridge of the tongue. The sling formed by the exter- 

 nal inouals in front of the radular sac is not attached to the latter in any way. These three 

 muscle: do not have their origins upon any hard part, such as the jaws, but in a sort of tendinous 

 mass (T) which is tirmlv attached to the floor of the mouth and the muscular membrane desciibed 

 a ishort time ago. From this tendon a short, strong muscle, the ""g^^^l P^-"^^J^*«„;\^^f^^ 

 forward and outward under the edge of the opening muscle of the ]aws (F g. 3-1 8) to the pi o- 

 iecting point of the inner flange of the upper jaw. It would seem as it he only eftect of the 

 contract on of this muscle must be to pull the origin of the Ungual muscles forward possibly 

 permitting a greater extension of the tongue; the combined effect of the contraction of the inter- 

 nl u d e^tenial lingual and the radular muscles would be to pull the tongue and the radula up 

 ndback; a simultan^eous contraction of the lingual protractor would possibly keep the radu a 

 ightly p essed against the object it was rasping. The sling formed by the external Ungual is 

 ft attached to th'e radular sac in any place. The integument whidi si^^ports ^^^^rU^ 

 of the radula is stronglv supplied with muscle fibres running outward and downward to the sides 

 of the jaw; the disti^.f muscles going to the.se parts have been mentioned. While these mu.scle 

 ; e comparatively weak, they probably are protractors oi the tongue^ I^cn- t^-^^^^i^ 

 the radula indicates that its rasping or pulling effect is produced only when the tongue is thiust 

 upward and backward, and only in this motion would great resistance be encountere^. Conse- 

 cuentlv the muscles which pull the tongue back are large and strong. As no great resistance 

 would be encountered in pulling the tongue forward, the small --t^^"-^^\*V ilSl 

 ment seem to be sufficient. The integument of the tongue is supplied with a weak longitudinal 



'"''' stdTmuscles extend into the salivary lobes from near the origins of the lingual muscles. 



The walls of the mouth cavitv are formed by the inner flange of the upper jaw, except 

 ventrallv. From the floor of the mouth the tongue, bearing the radula and J,"'" ^^^ ^f/^^^;^^;^^ 

 project 'into the cavity. In front of the tongue are two processes (Fig. 32, PP and AP), one 

 b hind the other, whii are really upfoldings of the floor of the mouth The an e-r proc..s 

 is 8 millimeters in height and 12 millimeters in width, covered with papilla- upon both .^ ^es, the 

 papilhe upon the anterior side being much smalle. than tho.se upoii the Vo>^^ov^^ The 

 posterior of the two processes is slightly higher and considerably wider ^^-1 the x.^. - I^ 

 base is carried up a short distance on each side of the tongue. This process beais papiU* onij 

 .on h'edge and the posterior side; the anterior surface is covered with hue t-nsvei.e ridges 

 The tonjue is a large organ which occupies most of the space within the m^uth (Fig. 32. Tn) 

 It is about ^22 millimftersln length, 10 millimeters in width, and l\""j ^^ [^^ ^ ^^"^i^^; 

 Anteriorly the tongue rises abruptly and with somewhat of an overhang to its full height. 1^ oi 

 nearly ha f its length it maintains this height, then slopes gradua ly to the floor of the mouth 

 innJliatelv in front of the cBsophageal opening. The shape of the tongue may vary, e g it 

 mav slope downward and forward to the opening of radular .sac and then sloping down and back^ 

 The sides of the tongue are nearly vertical and are entirely free from papillae. The dor^a .su face 

 of the tongue, on the other hand, is thickly covered with large papi he. Just in front of the 

 cesophacreal opening are a number of peculiarly long and slender papillae. 



Th^ anterior surface of the tongue is covered by the radula. (Fig. 32, R ) The radula passes 

 up over the tip of the tongue and then almost immediately bends^downward again and is lost to 

 vLin the radular sac. The radular .sac pa,sses downward and a Uttle ^-kward unde th 

 ntec^ument of the point of the tongue till it reaches the under side of the tongue, where it abruptly 



