500 GKOFFREY SMITH. 
Acanthotelson (text-fig. 62) appears to me to oceupy a 
different position, and | am doubtful if it is rightly associated 
with the Syncarida at all. The thorax only possessed seven 
free segments, and the thoracic limbs show no trace of being 
biramous. The abdominal limbs are expanded, flabellate 
structures, and the tail-fan is elongated and sharply pointed. 
The only resemblance of this creature to the Syncarida is the 
very general feature that a carapace is absent, and there is 
really no reason for supposing that this fossil is not a 
generalised Amphipod. ‘I'he condition of the eyes is un- 
known. 
(B) Segmentation. 
Perhaps the most striking feature of the Anaspidacea is 
the entire absence of acarapace. In Anaspides tasmanie 
there appear to be eight free thoracic segments and there are 
undoubtedly six abdominal segments, without counting the 
telson. The true segmental value of the first thoracic 
seoment behind the head has, however, been called in ques- 
tion by Calman (8). He inclines to the view that the groove 
separating the head from what appears to be the first segment 
corresponds to the cervical suture in the Decapcda, and that 
the apparent segment behind this suture really represents 
three segments belonging to the two pairs of maxille and the 
first thoracic limbs. The compound nature of the segment is 
possibly indicated by the definite lateral suture which crosses 
it on each side in the position shown in text-figs. 1 and 4. 
Whether this anterior segment represents three fused 
segments or not, a question which may remain open to doubt, 
it is certain that its freedom from the head is far more 
complete in Anaspides than in any of the higher Malacos- 
traca, and that the process of cephalisation has not gone so 
far in Anaspides as in the latter. Since, also, there is no 
doubt that the first thoracic segment is incorporated in, 
though it may not entirely represent, this segment, we will 
speak of it as the first thoracic segment. 
