490 Dr. W. T. Caiman — *S 'y near icla from Coal-measures. 



relations in this respect. The fifth somite appears to be the shortest, 

 and at all events the side-plates of this somite are distinctly narrower 

 (antero-posteriorly) than those of the adjacent somites. The seventh 

 somite appears to be the longest. On the dorsal side the second, 

 third, fourth, and fifth somites are seen each to overlap the somite in 

 front, while the sixth, seventh, and eighth, like those of the abdomen, 

 overlap backwards. It is probable that the fifth somite overlaps both 

 in front and behind, but this cannot be distinctly seen. 1 In one other 

 respect also the fifth somite divides the thorax into two regions, for 

 the second, third, and fourth somites have the lower margin of the 

 side-plates rounded with a slight obliquity forwards, while those of 

 the sixth, seventh, and eighth are pointed and directed backwards. 

 The lower margins do not seem to overhang the bases of the legs. 

 The depth of the thoracic somites is about 2 mm. 



The abdomen, excluding the telson, is a little shorter than the 

 thorax. The first five somites do not differ greatly in size, the length 

 of each being a little less than that of the posterior thoracic somites. 

 The pleural plates are rounded and slightly produced backwards. 

 The sixth somite is a little more than half as long again as the fifth 

 and of equal depth anteriorly, narrowing a little posteriorly. 



The telson is not well displayed in any of the specimens. It is 

 shorter than the uropods, broadly rounded at the tip, and fringed with 

 spines. Its great apparent thickness at the base in side view may be 

 due to crushing. 



Appendages. — In several of the fossils a very distinct impression is 

 seen in front of the head above the base of the antennule. There can 

 be little doubt that this represents the eye-stalk, although the form of 

 its distal end is not clearly defined in any of the specimens. It tapers 

 slightly towards the base and appears to have been at least twice as 

 long as its greatest diameter. 



The antennule has the three segments of the peduncle successively 

 diminishing in thickness; the first is the longest and the second the 

 shortest. The fiagella are incomplete in the specimen figured, but 

 another specimen shows both of them to be at least twice as long 

 as the peduncle. 



The antenna shows distinct traces of a large lamellar exopodite, but 

 in no case can its complete outline be traced. The last segment of the 

 peduncle appears to bear a prominent lobe fringed with setse, but it is 

 possible that this is really the tip of the overlying exopodite. The 

 flagellum is about as long as the body ; its segmentation is very distinct 

 in some specimens, the segments being broader than long and slightly 

 oblique near the proximal end and becoming longer than broad towards 

 the tip. 



Impressions of the mandibles (Fig 2, A) can be seen in many of the 

 fossils. The 'body' of the mandible is large and its obtusely pointed 

 proximal end is overlapped by the side-plate of the head; distally it is 

 produced into a narrow incisor process, and it forms on the anterior 

 margin a marked shoulder where the palp may have been articulated. 



1 In Anaspides the fourth thoracic (third free) somite overlaps both in front 

 and behind. I have not been able to determine the overlap of the somites in 

 the other recent genera. 



