28 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 21, 



the equivalent zone of A. Burgundke in Franco are veiy few in 

 number ; that the Azzarola strata in Lombardy containing Avicvla 

 contorta have a great Madi^epore-becl whose species, although differing 

 from those of the higher members of the Infra-lias, possess the 

 general facies of the fauna ; and that the Madreporarian fauna of 

 this period, although rich in individuals and species, does not appear 

 to have been luxuriant. 



3. On some Points in tlie Structuee of the XirnosuEA, liaving 

 reference to their relationsJiij) with the EuRTrTEEin^E. By Henry 

 Woodward, Esq., E.G.S., P.Z.S., of the British Museum. 



[Plates I. & II.] 



So long since as 1849 * Professor M'Coy made the proposition to 

 unite in one tribe of the order Entomostraca the recent and fossil 

 Limuhdse and the extinct species of Pterygotus and Eurypterus. *'The 

 tribe Poecilopoda,'' he observes, " are to be distinguished from other 

 Entomostraca by having crustaceous, didactyle, ambulatory tho- 

 racic feet, as well as membranous, respiratory abdominal ones.'* 

 Professor M'Coy divides the Poecilopoda into two divisions : — 1. Li- 

 mulidoQ — Limulus; and 2. Eurypteridae — Eurypterus, Pterygotus, and 

 Bellnurus. He subsequently furnished a restoration of Pterygotus 

 prohlematicus, in illustration of his view of the anatomy of this 

 ancient fossil remain f. 



It is not surprising that Professor M'Coy should have failed to 

 establish this order, since it was shown by Professor Huxley X to 

 be founded upon an erroneous interpretation of the fossil remains ; 

 nor can it be doubted that the arrangement was based on conjecture 

 rather than upon any minute acquaintance with the anatomy of 

 these extinct forms of Pterygotus and Eurypterus, then only known 

 in England by extremely fragmentary remains. 



The researches, too, of Professor Huxley § into the anatomy and 

 affinities of the genus Pterygotus (in 1859) do not favour M'Coy's 

 view of their classification under a common order or tribe with Li- 

 mulus, although he does admit that they possess several very im- 

 portant points of structure in common with the latter. 



'' The Poecilopoda " {i. e. Limulidee), observes Professor Huxley §, 

 " are, I believe, the only Crustacea which possess antennary organs 

 like those of Pterygotus, and, like them, have the gnathites converted 

 into locomotive organs, want the appendages to the sixth abdominal 

 somite, and present on some parts of the body a remotely similar 

 sculpture. In this order, however, we find but a small labrum, a 

 rudimentaiy metastoma, a very differently constructjed body, and a 



* Ann. & Mag. Nat. Hist. 2nd ser. vol. iv. pp. 393, 394. 

 t Lyell's Manual of Elementary Geology, 5th. edit. 1855, p. 40. fig. 543. 

 I " On the Anatomy and Affinities of the genus Pterygotus,^' Memoirs of the 

 Geological Survey of Great Britain, Monograph I. (1859) p. 7. 

 § Op. cit. p. 34. 



