790 MR W. T. CALMAN ON 



of several important characters which point, as it were, in various directions towards 

 presumably far distant branches of the Crustacean stem. Its auditory organs are those 

 of a Decapod, the general form of the body is more that of an Amphipod than a Schizo- 

 pod, while such characters as the double epipodial lamellae, the coxal lobes of the 

 maxilliped, and the remarkable dorsal "ocelli" (if such they be) are without parallel 

 among the Malacostraca. 



COMPARISON WITH PALEOZOIC FORMS. 



But Anaspides becomes still more striking in its interest when we pass from the 

 limits of the recent fauna to seek comparisons with fossil forms. Among Palaeozoic 

 Crustacea there are several forms whose systematic position has hitherto been a complete 

 puzzle to palaeontologists. The genera associated together by Packard to form the 

 groups Syncarida and Gampsonychidse agree with each other and with Anaspides, and 

 together with it stand apart from all other Crustacea whatsoever, in combining with the 

 absence of a carapace, the presence of distinctly podophthalmate characters in antennules, 

 antennae, and tail-fan. These fossil forms had been compared by various palaeontolo- 

 gists with the Ampliipoda, the Isopoda, and the Macrura, while Packard emphasised 

 more particularly their affinities with Schizopods. With this preliminary statement we 

 pass to a detailed comparison of Anaspides with the Palaeozoic genera. 



PALjEOCARIS. 



Palzeocaris typus was first described in 1865, by Meek and Worthen, from the 

 Coal Measures of Illinois.* Packard, in 1886,t redescribed the species, and gave a 

 restoration, which we reproduce (Plate II. fig. 15), certain characters being added from 

 a later paper by the same author.^ It is manifest from the figure that Paleeocaris 

 resembles Anaspides in general shape. The body is uniformly segmented, there 

 being seven distinct segments in the thorax, while a carapace is completely 

 lacking. The first five abdominal segments carry downwardly projecting pleura, the 

 sixth segment being elongated and apparently cylindrical. The eyes are unknown, but 

 the antennules have the three-jointed peduncle strongly developed and carrying a pair 

 of flagella, of which the longer is one-third or one-half the length of the body. The 

 antennae have a broad scale or exopodite, extending nearly to the end of the peduncle, 

 rounded at the end, and edged with setae. Two joints of the peduncle are seen, and the 

 nagellum is as long as the body. Of the thoracic appendages only six pairs are shown 

 in the restoration, but it is stated in the text that the first two pairs in front of these 

 arc "gnathopods like those of existing Schizopods, especially Petaloiihthalmus" though 



* Proc. Acad. Nat. Sc. Philadelphia, 1865 ; also, Rep. Geol. Survey, Illinois, iii., 1868. 



+ Mem. Nat. Acad. Sci. Washington, iii. (2), 1886. A preliminary abstract in Amer. Naturalist, xix., pp. 790-792, 1885. 



X Proc. Boston Soc. Nat. Hist., xxiv., pp. 211-213, 1889. 



