1866.] WOODWAED STEUCTUEE OF XIPHOSUEA. 29 



large number of appendages, both thoracic and abdominal — charac- 

 ters which eifectually preclude the association of the extinct Crus- 

 tracea under discussion with this type." 



Professor Huxley adds in a foot-note*, " If the abdominal 

 somites of the Carboniferous Belinurus &c. were really free, they 

 would present a certain approximation to the Pterygoti. Indeed 

 the evidence that these Carboniferous Crustacea were true Poecilo- 

 poda is to my mind anything but conclusive." 



The later researches of Professor James Hall, State Geologist to 

 the State of New York (U. S.) f, into the structure and affinities of 

 Eurypterus have led him to the conclusion that a close affinity exists 

 between Eurypterus, Ftetygotus, and Lijimlus ; and he also cites the 

 opinion of Professor Agassizt, "that the Eurypteri are closely re- 

 lated to Limulus, belonging even to the same order." 



" He regards the antennal system as entirely absent. The organs 

 of locomotion belong to the cephalic region ; and while externally 

 they perform the functions of feet, they are, at the base, organs of 

 manducation. The central organ [PI. II. fig. 8, «], indicated as a 

 locomotive appendage [' opercidmn ' of Professor Huxley (see Med. 

 Times & Gazette, 1857), Professor Agassiz regards as similar to the 

 appendage attached to the membranaceous feet, behind the swimming- 

 feet of Limulus [PI. II. fig. 7, a'], and instead of being double, is anchy- 

 losed as in young Limuhts^' §. 



Professor Kieszkowski |1 (in Russia) appears to have arrived, about 

 the same time as Professor Hall (1859), at somewhat similar con- 

 clusions, only that he has made out a series of three thoracic mem- 

 branous plates all sculptured upon their surface. This could not be 

 the case, however, had they overlai^ped each other as in the recent 

 Limidus ; for surfaces that are covered by other overlying organs 

 are destitute of ornamentation. 



Much later (i. e. in 1863) I made au examination of these forms, 

 and, without being thoroughly acquainted with the foreign biblio- 

 graphy of the subject, I arrived independently at the same con- 

 clusion with Professors Agassiz and HaU %. In 1864 and 1865 I 

 continued my researches; and some of the results have abeady 

 appeared in the Journal of this Society and elsewhere **. 



Having devoted some time to the. examination of the (so-called) 

 fossil Limulidse of the Coal-measures, I think I shall be able to show 

 that we have evidence of some, at least, of the intermediate forms 

 that were absolutely needed in order to establish a relationship be- 



* Op. «Y.p.34. 



t Nat. Hist. New York : Palc^ontology (1859), vol. iii. p. 393. 



X Op. cit. p. 394. § Op. cit. 



H Archiv fiir die Naturkunde Livonia, Esthonia und Kurlands, 1st series, vol. 

 ii, p. 299, plB. 1 & 2: Dorpat, 1859. 



^[ See the Intellectual Observer for 1863 (vol. iv. p. 229). 



** See (a) Geol. Mag. vol. i. p. 196, pi. x., and p. 239. See also {h) Lyell's 

 Elements of Geology, 6th edit. (1865), p. 524, fig. 591. See also {c) Quart. Journ. 

 Geol. Soc. 1865, vol. xxi. p. 482, pis. xiii. & xiv. See also (d) British Association 

 Beports, 1864-65, Bath and Birmingham. 



