78 ART. 4. — N. YATSU : 



These muscles attach themselves to the ventral body wall 

 very near the median plane a little posterior to the occhisor 

 anterior and at the same level as the anterior end of the otocysts. 

 They diverge as they go backward and pass the furrow between 

 the posterior dorsal and ventral lobes of the liver. They finally 

 secure their insertion at the angle made by the lateral and the 

 dorsal body walls. 



The Obliqui medii {obi. med.) (Wood-cut B, PL VIII., 



Fig. 128). 



These are composed of three stout muscles peculiar to Lingula. 

 They have their origin on the ventral body wall on either side 

 of, and not far from, the median plane, and from these portions 

 they decussate right and left securing their attachment to the 

 dorsal valve near the insertion of the obliquus internus. 



I was unable to discover in living specimens or in sections a 

 thickened muscular ridge on the dorsal side of the stomach which 

 Brooks supposes " to connect the stomach with the lining of the 

 dorsal valve " (p. 61). 



m. Peduncle. 



The peduncle makes its appearance at the 6 p. c. stage (PL 

 V., Fig. 79, pd.) as an elevation of the inner layer of the ventral 

 lobe of the posterior mantle, a little to the right of the median 

 plane of the body. The elevation is elliptical, measuring 20/' 

 in length and 30 /^ in breadth (PL VII., Figs. 118, 119). Into 

 this elevation there leads out from the body cavity an evagination 

 which gives rise to the peduncular cavity. At the 7 p. c. stage 

 the peduncle is circular (PL VI., Fig. 83). With age it increases 



