SPECIMENS OF TRIARTHRUS. 157 
which really converge in an anterior direction. Between the ridges are shallow canoe-shaped 
depressions, which have the appearance of areas for the insertion of muscles. 
Measurements: Length, 31 mm. ; width at back of head, 15 mm. ; distance, in a straight 
line, from point of insertion of the right antennule to its tip, 14.25 mm.; it projects 12 mm. 
beyond the cephalon. 
Specimen No. 218 (pi. 6, fig. 3; text fig. 43). 
This specimen is a large one, developed from the lower side, but retains only the endopo- 
dites of a few appendages. The cephalon and anterior portion of the thorax are missing. 
Professor Beecher had a drawing made to show the appendages on the right-hand side 
of the last two segments of the thorax, seen of course from the ventral side. This drawing 
shows well the broadening of the basipodite, ischiopodite, and meropodite, while the coxopo- 
dite is thick and heavy, and the inner end of the gnathobase somewhat rugose. Almost 
Fig. 43. — Triarthrns 
becki Green. Drawing 
to represent the writer's 
interpretation of the ap- 
pendages of specimen 
218. Drawn by Miss 
Wood. X 10. 
every segment of the endopodites has one or more pits for insertion of spines, these being 
along the anterior or posterior margins. The exopodites lack the seta?, but show no unusual 
features. 
Specimen No. 222 (pi. 4, fig. 5). 
Illustrated: Amer. Jour. Sci., vol. 47, 1894, pi. 7, fig. 3 (drawing). 
A small specimen, developed from the lower side, and used by Professor Beecher to 
illustrate the form of the segments of the endopodites of the pygidium. In addition to this, 
it shows very well the form of the endopodites of the thorax. All of the appendages on 
the specimen are shifted to the left of their normal position. This specimen differs from 
most of the others in that the segments of the endopodites do not lie with their greatest 
width in the horizontal plane, but were embedded vertically, with the posterior edge down- 
ward. From this circumstance they retain their natural shape, and it is seen that they are 
naturally flattened, with about the same thickness in proportion to length and width as in 
some of the modern isopods (Scrolls, for instance). In even the most anterior of these 
endopodites (that of the second segment) the ischiopodite, meropodite, and carpopodite are 
