360 PALAEOSTRACA. 



A striking feature in some of the forms (Eurypterida) in this group is the scale- 

 like marking of the body-i)lates. 



A homology is naturally suggested, and has been carried out by Ray 

 Lankkstek, between the coxal glands of the Arachnida and Xiphosura and a 

 pair of Crustacean nephridia. This could only apply to the shell-gland, which 

 belongs to the segment of the second maxillae, i.e. to the fifth linili-bearing 

 segment. We should then have to homologise the chelicerae of the Arachnida 

 with the first pair of antennae of the Crustacea, an assumption which seems to 

 us somewhat daring, and not sufficiently supported by the structure and 

 development of the brain in the two groujjs. There is the less need for a 

 homology between the shell-gland of the Crustacea and the coxal gland of 

 Limidus and Scorpio, as Ave have to imagine each body-segment originally 

 provided with a pair of glands of this kind, an assumption which appears to be 

 justified by a comparison with Fcrijicitus.* 



LITEEATURE. 

 I. Trilobita. 



1. Barrande, J. Systeme Silurieii du Centre de la Bolierae. 



Prar/?te et Paris. Premiere Partie. Tom. i. 1852. And 

 Sup]ilement Tom. i. 1872. 



2. Ford, 8. W. On some Embryonic Forms of Trilobites from 



the Primordial Rocks at Troy, N. Y. Amer. Journ. Sci. (3). 

 Vol. xiii. 1877. 



3. Ford, 8. W. On additional Embryonic Forms of Trilobites 



from the Primordial Eocks of Troy, jS". Y., etc. Amer 

 Journ. Sci (3). Vol. xxii. 1881. 



4. Matthew, G. F. Sur le dcveloppement des premiers Trilobites. 



A7i7i. Soc. Roy. Malacologique de Belgique. Tom. xxiii. 1888. 



5. Walcott, C. D. The Trilobite: New and Old Evidence relating 



to its Organisation. Bull. Mus. Camp. Zool. Harvard Coll. 

 Camhridge. Vol. viii. 1880-1881. 



6. Walcott, C. T). Fossils of the Utica Slate. Tram. Alhann 



Inst. Vol. X. 1879 (1). Contains statements as to the 

 metamorphosis of Triarthrus Becki. 



7. ZiTTEL, K. A. Handbuch der Paliiontologie. Bd. i. Abtheil. ii. 



Miinclten and Leipzig, 1885. 



[* The new discoveries of the antennae and limbs of a Trilobite (Triartliriis) 

 have advanci'd our knowledge of these fossils and of their affinities so greatly, 

 that the student nnist not rest content with the foregoing. The recent observa- 

 tions of Bei:( HEK ami Bernakd (App. to Lit. on Trilobita, ISTos I., II., III., IV.) 

 have taken the point off manj^ of the author's comments on the Aaluable infor- 

 mation given above. The text is translated as it stood on account of the matter 

 it contains, and the reader is merely referred to the more recent works on 

 the subject. This seems to be the only alternative to re-writing the whole 

 chapter. ^ — Ed ] 



