162 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
projects into the lumen in a prominent crest, the lateral-valve ridge 
(lor), which terminates posteriorly as the lateral pyloro-intestinal 
valve. These valves are united with the dorso-lateral and the min¬ 
ute, median, dorsal valve for a space (pi. 9, fig. 58, do, dlo, lo) so 
that these valves enter the intestine as a continuous curtain. 
Throughout the zoea phase, the stomach (pi. 9, fig. 55) has a 
deep and narrow cardiac portion, which is not longer than the pylo¬ 
rus, and chitin is poorly developed except on the smooth cardio- 
pyloric valve. There is no dorsal tooth ; the lateral teeth are simple 
and project upward instead of horizontally (pi. 9, fig. 48, It) ; the 
pyloro-intestinal valves are not united and are three in number, viz. * 
the paired laterals and dorsal. In the first zoea the pylorus is with¬ 
out pouches, but with the second stage an area on either side of the 
median pyloric valve becomes setose and in the fourth stage these 
areas are depressed to form the lateral pouches. The cardiopyloric 
and median pyloric valves are at first confluent, but become distinct 
with the second stage. A single oesophageal plate appears with the 
fourth stage. 
The stomach of the glaucothoe (pi. 9, fig. 56) may be regarded as 
transitional in type, its more elongate form, horizontal lateral teeth 
(pi. 9, fig. 51), and well developed lateral-valve ridges recalling the 
stomach of the adult. There are indications of a dorsal tooth ; the 
pyloro-intestinal valves are united; and a small dorso lateral valve 
(dlo) is added on each side. In other respects the larval characters 
persist. No metamorphosis occurs during the period except a 
change in the mutual relations of the openings from the livers and 
lateral caeca. 
The sixth stage has a stomach of adult type, but with the parts 
less specialized. The upper pyloric pouches are still wanting, and 
they are probably of late adolescent development. 
In the intestine of the Decapoda, it is generally accepted that the 
limits of the chitinous lining are coincident with the limits of the 
post- and mid-guts. But until this is supported by a larger body of 
evidence, it is perhaps better to use the purely descriptive terms 
“ chitinous ” and “ achitinous ” for the post- and mid-guts respec¬ 
tively. In the adult Eupagurus the achitinous gut is relatively 
shorter than usual, as the chitinous gut only extends into the ante¬ 
rior part of the abdomen. An unpaired caecum — first described by 
Swammerdam in 1737 — starts from the right side of the achitinous 
