E. A. Andrews — Anatomy of the Spider Crab. lo*/ 



From the month the sliort, wide oesophagus {oe) leads upward and 

 slightly backward to the large stomach, which lies partly above the 

 mouth and fills most of the cavity of the head region {g, fig. 1 ). The 

 stomach includes a large spherical anterior portion (c, fig. 19), the 

 cardiac region, and a smaller, cylindrical, posterior part (jy), the py- 

 loric region, which is inclined downward. Like the oesophagus it is 

 lined \vith a thin chitinous cuticle continuous with the external chiti- 

 nous body wall ; and which in the pyloric and posterior part of the 

 cardiac regions becomes folded and thickened to form the numerous 

 chitinous ossicles and ridges which make up the complicated grinding 

 and straining apparatus (figs. 17, 18). 



On removing the muscular walls of the stomach th(; chitinous cuti- 

 cle is seen to have a very irregular surface, the ossicles projecting 

 and deep cavities corresponding to some of the internal projections. 

 A deep dorsal, and deeper ventral cavity serve to make a constric- 

 tion between the pyloric and cardiac regions. 



The chief pieces of the grinding apparatus of the cardiac region 

 are three stout ossicles bearing internal, dark-colored, toothed prom- 

 inences. Of these a long, median one, the urocardiac ossicle (?<c, fig. 

 18), extends along the dorsal surface from the dorsal cavity in front 

 of the pylorus to near the center of the cardiac region, where it is 

 closely united to a small triangular ossicle, the cardiac ossicle (c), 

 which articulates on either side to a long transverse piece {pt), the 

 jtterocardiac ossicle, which at its outer end articulates to the supero- 

 lateral cardiac ossicle {si, figs. 17, 18, 19). This urocardiac ossicle 

 bears at its posterior end a blunt median tooth-like process with a 

 more acute one on either side of, and a little in advance of it (/, fio-, 

 18). The two supero-lateral cardiac ossicles complete the main part 

 of the grinding apparatus, being broad plates posteriorly jn-oduced 

 within the cavity of the cardiac region as stout, horizontal, lono-itu- 

 dinal ridges (r, fig. ] 7), armed with blunt, tooth-like prominences {t, 

 fig. 1 8). These ridges may be made to meet one another and, with 

 the toothed surface of the urocardiac ossicle which descends, must 

 aid in crushing the food. The large lateral ossicles above mentioned 

 articulate posteriorly with a pair of but slightly calcified plates, the 

 pyloric ossicles {^:>o, figs, 17, 18), which lie on the dorsal surface of 

 the anterior part of the pylorus and serve to connect these lateral 

 ossicles with the median, prepyloric ossicle (^j). This latter ossicle 

 forms the anterior face of the upper part of the pylorus and articu- 

 lates at its lower end with the urocardiac ossicle. These three me- 

 dian ossicles and three pairs of paired ossicles (including the pyloric 



Trans. Conn. Acad., YoL. VI, 1883. 15 July, 1883. 



