E. A. Andrews — Anatoniy of the Spider Crab. 109 



may be dividied into three dilations or pouches. The most anterior 

 of these and the largest, lies behind the praepyloric ossicle, and bears 

 on its upper surface the two pyloric plates and on each lateral sur- 

 face a slender ossicle (s, fig. 11) whose anterior end, is inserted between 

 the pyloric ossicle (^>o) and the superodateral cardiac ossicle [si). 

 The middle pouch is narrower and on a lower level than the first, it 

 bears four meso-pyloric ossicles. A pair of these lie along the upper 

 surface {ms, figs. 17, 18), one on either side of the median line, and 

 articulate at their posterior ends with a pair of somewhat triangular 

 transverse ossicles (ta). These latter are articulated to the upper 

 posterior processes of the lateral pyloric ossicles (Ij)). This lateral 

 pyloric ossicle on either side is a broad vertical piece, descending 

 across the compressed part of the pylorus, and is articulated by a 

 slender process at its lower anterior edge with the small plate (Zy fig. 

 17) forming the upper surface of the anterior part of the shelf-like 

 projection of the pylorus, while a process from the lower posterior 

 end joins it to the postero-lateral pyloric plate (^:>^j), fig. 17). At this 

 point of union a delicate, spatulate process projects from the wall of 

 the pylorus {^y, fig. 18), The posterior pouch is formed by the origin 

 of the chitinous lining of the intestine and is broader than the com- 

 pressed part of the pylorus, projecting on either side. Its anterior 

 edge is formed by an arch of five delicate uropyloric ossicles, a 

 curved median dorsal one {up^ fig. 17, 18) and two pairs of lateral 

 ones (up', up"), of which the lower are much the smaller. From this 

 framework a delicate chitinous cuticle extends backward a short dis- 

 tance into the intestine in the form of a funnel (/") open on the lower 

 side ; it is then reflected back on itself fiar more than half its length 

 and is attached to the muscular wall of the intestine. The folded 

 portion, which thus projects freely into the intestine, must form a 

 valve preventing the contents of the intestine from passing forward 

 into the stomach. Below this posterior pouch the lateral pouches (o) 

 connect with a pair of three-pronged ossicles ((7, fig. 17) forming the 

 posterior boundary of the pylorus and including between them the 

 opening of the bile ducts into the posterior end of the pylorus (h). 

 The horizontal upper surface of each lateral pouch or capsule is con- 

 tinuous with the broad, vertical, postero-lateral pyloric plate (pp) 

 which forms part of the wall of the compressed lateral portion of the 

 pylorus. These capsules are articulated anteriorly with a single 

 median, transverse, infero-pyloric ossicle {ip'), the anterior edge of 

 which articulates to a similar infero-pyloric ossicle (ip). This latter 

 ossicle is larger and forms the posterior boundary of the deep cavity, 



