Curton.—On Astacus fluviatilis and Paranephrops setosus. 161 
ossicles (pe) have much the same shape and position as in Astacus. The 
lateral teeth (lt) are large and reddish-yellow in colour. Anteriorly the 
teeth are large and distinct and there is one large tooth placed on one side 
of the row; posteriorly the teeth decrease greatly in size, but there are two 
or three rows so that they form an efficient grinding apparatus. Beneath 
the lateral teeth on each side there is a small, single, sharp tooth at the 
end of a long, thin, calcified bar. In a side view of the stomach (fig. 6) this 
tooth is seen to be also supported by a broad plate, the inner surface of 
which is thickly covered with short, stiff, plumose sete. On the raised 
edge of this plate, projecting from either side into the interior of the 
stomach, there is a row of sete similar to the others except in length. 
These stretch across and meet in the centre and appear to be for the 
purpose of stopping the food and forcing it to pass through the gastric 
armature already described. They (pl. XXI., fig. 6) are very long and 
slender, of the same size throughout almost the whole of their length, 
often slightly curved towards the end. The stem is unjointed and is 
covered with filaments, which are not much longer than the diameter of 
the stem itself. 
The pyloric portion of the stomach seems to be essentially the same as 
in Astacus. The cecum (pl XX., fig. 6 cw) appears to be variable, for 
though I have seen it quite distinctly in some specimens, I have been 
unable after careful search to find it in others. The cardio-pylorie valve 
(cpv) is present as in Astacus, and the transverse section of the pylorie 
region is so very much like that of Astacus that I have not given a figure of 
it.* At the opening of the pyloric sac into the intestine there are valves, 
one median, one above, and apparently only one on each side. 
From the pyloric end of the stomach the intestine passes direct to the 
anus on the ventral surface of the telson. There is no cecum in connection 
with the rectum as there is in the lobster, Homarus vulgaris.t 
At the sides of the stomach gastroliths were found in some specimens. 
These evidently differ much in shape according to their state of develop- 
ment, and when fully developed they differ considerably from those of 
Astacus. The side turned towards the stomach is either flat or slightly 
concave. The part which forms the convex side is doubled over so as to 
join with the flat or concave side, the junction between the two forms a well- 
marked nearly circular indentation. The flat or concave portion inside this 
ring is quite smooth. The convex side is more convex than the correspond- 
ing part in the gastroliths of Astacus, and it also differs in being quite 
* See “ The Crayfish,” p. 53, fig. 9 E. 
1 See Huxley and Martin's “ Practical Biology," p. 133. 
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