202 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



100, q) back of the heart, and usually on the right, some- 

 times on the left side of the intestine, and a straighter por- 

 tion which runs back from the coiled portion to open into 

 the intestine. 



7. The gastric mill. Notice once more the anterior and 

 posterior gastric muscles which inn from the cardiac pouch 

 to the carapace ; clean them off, and notice, in the wall of 

 the cardiac pouch a pair of stiff, white, calcareous rods 

 (Fig. 101, a), the pterocardiac ossicles, which meet each 

 other on the median line, while their slender, outer ends 

 run outwards and downwards onto the sides of the 

 stomach, where they join the cardiac later o-super lor ossicles 

 or zygocardiacs (Fig. 101, b). These incline backwards, 

 upwards, and inwards, and their hinder ends join a small 

 transverse bar, the pyloric ossicle (Fig. 101, c) which lies 

 near the posterior end of the stomach. The pterocardiac 

 and pyloric ossicles are joined to each other by a pair of 

 median gastric muscles (Fig. 100, c) ; and, removing these, 

 note that they do not lie on the surface of the stomach, 

 but that they roof over a deep, conical depression pro- 

 duced by an infolding of the stomach-wall between the 

 pterocardiac and pyloric ossicles. From the point of 

 union of the two pterocardiac ossicles, a stout bar, the 

 urocardiac ossicle (Fig. 101, d) runs downwards along 

 the anterior edge of this pit, while a much smaller pre- 

 pyloric ossicle (Fig. 101, e) runs from the middle of the 

 pyloric ossicle (c) along the posterior face of the pit, to 

 join the lower end of the urocardiac ossicle. 



Turn the stomach to one side, and, cutting the oesopha- 

 gus and intestine, remove it from the body, and notice in 

 a side view the large, thin-walled cardiac pouch and the 

 much smaller, thick-walled pyloric pouch. Carefully clear 

 away the layer of muscles which forms the greater part of 



