Dr. H. Woodward — Contributions to Fossil Crustacea. 533 



the Lithographic Limestone of Solenhofen, this new Cretaceous 

 Eryon from Niederlishna has the outer caudal plates of the tail 

 entire, whereas in the older Liassic form of Eryon it is divided across 

 by a transverse joint, as is also the case in the outer swimmeret 

 of the tail of Astacus, Homarus, Nephrops, and many other genera. 

 This genus is remarkable for the persistent character of its hastiform 

 telson, observable not only in the living genus Polyclieles, but also 

 in its Liassic predecessor, Eryon Barroviensis. Eryon Oppeli is the 

 only species with an ovately rounded telson ; and therefore probably 

 indicates it to belong to another genus. 



3. — Palceocaris Burnettii, H. Woodw., sp. nov. PI. XIV. Fig. 3a, b. 



The genus Palaocaris was proposed by Messrs. Meek and 

 Worthen, in the Proceedings of the Academy of Natural Sciences, 

 Philadelphia, in March, 1865, p. 48, for a remarkable type of Crus- 

 tacean obtained from near the base of the Coal-measures of Morris, 

 Grundy County, Illinois, U.S.A., having the "inner and outer pairs 

 of antennse of nearly equal length, the former each bearing a well- 

 developed accessory appendage ; the peduncles of both pairs being 

 shorter than the flagella. Head about as long as the first two 

 abdominal segments. Thoracic legs long and slender ; anterior pair 

 not chelate. Telson long, tapering and horizontally flattened ; 

 ' stylets ' with first joint very small, second double, and also flattened 

 horizontally." 



Only one species, Palieocaris typus, has been defined by Messrs. 

 Meek and Worthen. The authors describe the 

 " thorax " as " slightly wider near the middle 

 than the abdomen " ; and the " thoracic and 

 abdominal segments of nearly equal length " ; 

 the '• telson nearly as broad at the base as 

 the penultimate segment, tapering, and as long 

 as two and a half of the abdominal segments. 

 The ' stylets ' (or lateral caudal appendages, 

 sometimes called 'swimmerets ') with the first 

 joint very minute, second joint with each divi- 

 sion as long as the telson, and lanceolinear in 

 form, with pointed extremities and parallel 

 setigerous margins." 



This curious larval-looking genus of Crusta- 

 ceans and another genus found by these authors 

 Me^''&'wortiien. ^^ ^^® same locality and formation, which closely 

 resembles it, named by them, Acanthotelson 

 Stimpsoni (see our Plate XIV. Fig. 4) have been referred by Prof. J. 

 D. Dana, " to a group probably holding an intermediate position 

 between the typical Isopoda and the Amphipoda for which he pro- 

 posed the name Anisopoda." 



"This intermediate group, as first shown by Prof. Dana, is 

 characterized, like the Amphipoda, by having the three posterior 

 pairs of thoracic legs in one series, and the four antei'ior pairs 

 in another; while, as in the Isopoda, the branchiae are abdominal. 



