798 MR W. T. CALMAN ON 



in Anaspides, but as it seems to have been only imperfectly visible on the fossil, it is 

 possible that the restorer was guided to some extent in this point by the analogy of 

 Gampsonyx, in which a similar line is very distinct.* 



To sum up, Palseocaris resembles Anaspides closely in general form, in the number 

 of free segments of the body, in the absence of a carapace, in the general characters of 

 antennules and antennae, of the swimmerets, and of the tail-fan. Points of doubtful 

 agreement are found in the line which divides the two " segments " of the head, which 

 may possibly represent the cervical groove of Anaspides, and in the so-called " endopo- 

 dites " of the thoracic legs, which may correspond either to exopodites or to epipodial 

 lamellae, but which must be either one or other. Points of actual difference exist in the 

 arrangement of the last-named organs, which, whatever their nature, are arranged in a 

 single series, and are stated to be present on all the eight pairs of thoracic limbs, whereas 

 in Anaspides both exopodites and gill-plates are absent from the last pair of legs. It is 

 not improbable that some of these differences might be reduced, could the actual speci- 

 mens of Palseocaris be re-examined in the light of the information afforded by Anaspides. 

 Packard, throughout his papers, compares Palseocaris with the deep-sea Petalophthal- 

 mus and with no other Schizopod. Beyond the fact that the carapace in that very 

 aberrant genus is unusually small, we do not see any indication of a special affinity 

 between the two forms. 



GAMPSONYX. 



Gampsonyx Jimbriatus, from the Coal Measures of Saarbriick,t was described by 

 Jordan and v. Meyer in 18544 As will be seen from the figure (Plate II. fig. 17), 

 it resembles Palseocaris in the segmentation of the body, but the line which in that 

 genus divides the two "segments" of the head according to Packard is here more 

 distinct, so that there appear to be eight free thoracic segments behind the head. It 

 is very tempting to compare this with the condition found in Anaspides, but we have 

 above given reasons for thinking that the so-called " first thoracic segment " in that 

 form includes the region of the maxillae as well as that of the maxillipeds. In the 

 fossil form this does not appear to be the case, for the segment in question is narrower 

 below than above, and would apparently correspond to only one pair of appendages. § 

 Still the coincidence in the number of apparent segments in the two forms is a 

 very remarkable circumstance, and a re- examination of the fossils on this point is much 

 to be desired. 



The eyes of Gampsonyx are stated to be pedunculated. The antennules resemble 

 those of Palseocaris. The antennae have a large scale, rounded > at the tip, a three- 

 jointed peduncle, and a long flagellum. 



* The Palseocaris scoticus of Peach {Trans. Roy. Soc. Edin., xxx., p. 85, pi. x. 3) differs very markedly from the 

 American form in the arrangement of grooves on the head-region. It may possibly represent a distinct genus. 

 + These strata are now referred by some authorities to the Dyas. 

 t Uil" r d. Sti ivJcohlenformation von Saarbriicken. PalceontogrwpMca, iv., 1856. 



mrdax and v. Meyer remark that this segment varies slightly in length in different specimens. 



