MARSUPITES. 117 
centre, and is adapted for the reception of the 
clavicles. 
The clavicles are small, and of a semilunar form 
externally ; the upper edge is thick, nearly straight, 
and unites with the humerm ; the lowermost is 
rounded, and corresponds with the semilunar cavity 
of the scapula ; between these two surfaces, on the 
inside, is a trLngular space, the use of which is 
not at present known. 
The cuneiform or humeral bones, may be con- 
sidered as the first of the arms ; they have four 
articulations, and are attached to the clavicles by the 
two lowermost. Their upper margin forms two ob- 
lique surfaces, each divided by a longitudinal ridge, 
in the same manner as the first johit of the finger 
in the Bradford encrinite (^apiocrinites rotundus'). 
From this structure it may be inferred, that the 
arms were dichotomous ; and probably were sub- 
divided, and terminated in elongated tentacula, as 
in the crinoidea. On the inner surface of the 
humerus, a smooth space is observable, appearing 
like a continuation of the triangular interval, on 
the corresponding part of the clavicle : this may be 
the articulating surface for the attachment of the 
pectoral bones. 
The reniform ossicula^ or pectoral bones, are 
united to each other by their upper and under 
surfaces, both of which are divided by a ridge, 
into two depressions. In the only specimen, in 
which these bones remain, the respective parts 
have sufiered so much displacement, that their 
mode of arrangement is no longer distinguishable : 
there is, however, reason to conclude, that in the 
I 3 
