Dr. H. Woodtvard — On the Genus Cyclus. 5-33 



Without maintaining that the pair of large rounded prominences, 

 observable in most of the specimens near the anterior border, are 

 eyes, there is evidence both in Figs. 7 and 8, PL XV., of the 

 presence of much smaller, and probably stalked, eyes near the front 

 of the head. The evidence of antennge-like organs, in situ, attached 

 to the part which I designate as the front of the shield (represented 

 on Plate XV. Figs. 4, 5, and faintly on Fig. 6), seems to me con- 

 clusive that this front, or upper border, as figured by me, is 

 indubitably the head. 



Mr. Peach mentions that where the dorsal shield, in his Cyclus 

 testudo, " has been broken away, so as to expose the interior of the 

 sternal portion to view, six triangular plates on each side, divided 

 from each other by deep sulci, are seen to converge upon an oval 

 sternum." These plates, he considers, " are the coxae of limbs." 



In discussing the question of the anterior and posterior ends of 

 Cyclus, as raised by Peach, the following points must be taken into 

 consideration : — 



1. The large pair of jointed appendages at one end, when taken 

 in conjunction with the entire absence of any prolongation of the 

 body beyond the circular shield at either end, suggests that this is 

 the head, and that these appendages represent a pair of swimming 

 antennas (ant. 2), similar to those of the Phyllopoda. 



2. This is further strengthened by the arrangement of the radiating 

 ventral plates at the opposite end of the body, which Peach suggests 

 are enlarged coxee. If the homology be the true one, which seems 

 pi-obable, then a comparison either with Arachnida or Crustacea, 

 results in the same conclusion, for, in any of these Arthropods, 

 where the limbs converge towards the mouth, or towards the sternum, 

 we find them tending to meet in the middle ventral line, behind 

 these structures, and not in front, as would be the case in Cyclus if 

 Peach's view as to the anterior end of the body were the right one, 



3. The Eye. — A (paired) small appendage, having somewhat the 

 form of a stalked eye, but showing no facets, is present near the 

 anterior margin of the shell (see PI. XV. Figs. 7, 8). 



Appendages. — The first visible appendages consist of one large 

 jointed pair, extending outwards from the anterior end of the 

 carapace. They suggest, from their position and development, the 

 second pair of antennas of the Navplius-stage of the Phyllopoda, or 

 of the adult Cladocera. No special mouth-parts are visible. 



The remaining appendages, which possibly represent both the 

 jaw-parts and anterior thoracic limbs of the higher Crustacea, 

 appear to be 6-7 in number, each of which was provided with a 

 greatly-developed basal joint radiating outwards from the mid-line, 

 and probably had a wide attachment, which may account for their 

 remaining in situ. The enlarged joints of the legs pressed against 

 one another, and covered the ventral surface of the body everywhere, 

 save in the centre, which was occupied by a V-shaped plate, towards 

 the pointed extremit}^ of which all the basal joints of the limbs 

 converge. Distally each limb presents two small plates. The rest 

 of the limb is lost in most specimens. 



