255 
1916-17.] Experiments and Observations on Crustacea. 
to the lateral aspect, the medial part of the proximal end of the segment 
ending in a thin edge which becomes continuous with the articular 
membrane. The bearing surface, prolonged beyond the rest of the segment, 
shows three smooth areas, all continuous, which fit against the bay-walls 
and the articular spur of the coxa. Viewed from the lateral (or postero- 
lateral) aspect (I here describe the arrangement in one of the perseopods 
the gnathopods show unessential variations from type) this portion might 
remind one of the posterior aspect of the distal end of the human femur — 
see fig. 4. It has two rounded condyles , the anterior more prominent than 
Fig. 4. — Proximal end of basipodite of second left perteopod 
of Glyptonotus, seen from postero-lateral aspect. x 4. 
This basipodite corresponds to the coxal foramen shown 
in the previous figure ; note, however, the difference in 
magnification. 
a, tendon of anterior extensor muscle ; b, anterior con- 
dyle ; c, coronoid fossa ; cl, tendon of posterior extensor 
muscle ; e, intercondylar ridge ; /, posterior condyle ; s, 
sesamoid calcification. 
the posterior, separated by a depression. There are great and essential 
differences, however, from the distal articular extremity of the femur. 
Stretching across the hollow between the condyles, and at a lower level 
than their upper ends, is the previously mentioned knife-edge or inter- 
condylar ridge , a slight groove in which, the intercondylar groove, bears 
against the concavity of the hook on the articular spur of the coxa. The 
posterior aspect of the anterior condyle and the anterior aspect of the 
posterior condyle are also smooth, as indeed is the whole interior of the 
intercondylar hollow. Over a less area the anterior aspect of the anterior 
and the posterior aspect of the posterior condyle are also smooth. Thus 
the whole lateral aspect of the proximal extremity of the basipodite is 
modelled to correspond with the lateral aspect of the articular foramen of 
