until Modern Representatives. 387 



Antennules. — These have three stout basal joints, measuring 

 together 5 mm. in length, of which the first is the broadest, the second 

 is very short, while the third, or distal one, is the longest ; each bears 

 a pair of multi-articulate flagella, the outer one being 10 mm. in length, 

 and the inner and smaller one is only 5 mm. long. 



AntenncB. — The antennse are more robust than the antennules ; the 

 three basal joints together are 7 mm. in length, and the third joint 

 bears a large oblong spatulate scale, or exopodite, fringed with setae. 

 The single flagellum is fully 8 mm. in length. 



Mandibles and maxillcB. — The mandibles and maxillae cannot be seen 

 in the fossil ; if preserved, they are hidden from view by matrix. 



Post-cephalic segments. — Assuming that the first thoracic segment 

 is coalesced with the head, there are seven free thoracic segments 

 behind the head, the three most anterior of which are each about 



3 mm. long and 3 mm. deep ; those which follow gradually increase to 



4 mm. in length and 5 mm. in depth. The lateral margins of the 

 anterior segments are broadly rounded, while the fi.ve abdominal ones 

 which succeed them gradually increase in depth and become more 

 pointed and slightly falcate posteriorly. 



Appendages. — The first free ( = to the second) thoracic segment 

 carries a pair of legs or maxillipeds (endopodites), the three first joints 

 of which are short, followed by a larger one (the meros), which is 

 about equal to the three proximal joints in length, and is broadest at 

 its distal end ; two smaller joints and a claw follow. Apparently there 

 was no exopodite developed on this limb, or, if present, it may have been 

 rudimentary, but it cannot be detected. Each of the four segments 

 which follow carries a pair of appendages about 10 mm. in length, 

 having a short, broad coxal joint, followed by a basipodite, which 

 supports on a slender joint or branch a multi-articulate setose exopodite, 

 and an endopodite in the form of a seven- or eight- jointed slender leg, 

 of which the carpus aj)pears to be the longest joint, ending in a single 

 claw or nail. The basal joint of each of these four pairs of appendages 

 probably also bore a pair of ovate-oblong branchial lamellae, but these, 

 being exceedingly delicate structures, are not clearly discernible in the 

 clay-ironstone matrix, but of their actual existence in the fossil I have 

 little doubt. 



The two pairs of limbs, borne upon the hindmost (seventh and 

 eighth) thoracic segments, do not appear, like the earlier four which 

 preceded them, to have possessed the multi-articulate setose exopodites, 

 but only the slender limbs (the endopodites), similar in character to 

 those borne by the more anterior segments. 



Ahdominal series. — The five most anterior segments of the abdomen, 

 as already stated, are deeper and have more pointed lateral margins 

 than the thoracic ones which preceded them. These had each a pair 

 of slender, bifid, many- jointed, setose swimming appendages, borne 

 upon a stronger basal joint, articulated with the antero-lateral border 

 of each of the five segments. The sixth segment is more or less 

 cylindrical in form, being 5 mm. in depth and 5 mm. in length, and 

 slightly narrower posteriorly, somewhat ridged dorsally, and grooved 

 and ridged laterally to give firmer attachment to its appendages ; 

 these form, with the ' telson,' the tail-fan or uropods. On the central 



