at eal oa 
OF THE AMERICAN KING-CRAB. 461 
expanded by Mr. Woodward *, may or may not meet with general acceptance, it is plain 
that Limulus has closer affinities with Pterygotus and other Eurypteroid Crustacea of palæ- 
ozoic age than with the Tribolites. My aim, therefore, in finally selecting, in 1843, Limulus 
for anatomical research reflecting light on the organization of palæozoic Crustacea, is 
equally fulfilled by the subsequent discoveries of Agassiz +, M'Coy t, Hall $, Niesz- 
kowski ||, Salter Y, Huxley Y, and Woodward **, of extinct Crustacea of as high anti- 
quity as the Tribolites, and more closely represented by Limulus. I doubt not therefore 
that the following illustrations of the structure of their lingering representative will be 
acceptable to Palzeontologists as well as to Comparative Anatomists. 
The contributions to the anatomy of Limulus previously made will be noticed in con- 
nexion with the sections to which they belong ++. 
$ 2. External Characters.—M.y remarks on this head need be few, and bear mainly on 
the intelligibility of the anatomical details. 
* * Reports and Proceedings of the British Association, Edinburgh, August 1871. Mr. Woodward exemplifies 
his views by the following concise parallel :— 
* Order MEROSTOMATA, Dana. 
* Suborder EURYPTERIDA. E * Suborder XIPHOSURA. 
* Ex. Pterygotus (Fossil, extinct). * Ex. Limulus (Fossil, and living). 
* ]. Eyes sessile, compound, * ]. Eyes sessile, compound, 
2. Ocelli distinctly seen. 2. Ocelli distictly seen, 
3. All the limbs serving as mouth-organs. 3. All the limbs serving as mouth -organs. 
4. Anterior thoracic segments bearing branchis or 4, All the thoracic segments bearing branchiæ or 
reproductive organs. reproductive organs. 
5. Other segments destitute of any appendages. Other segments destitute of any appendages. 
6. Thoracie segments wnanchylosed. . Thoracic segments anchylosed 
. Abdominal segments free and  well-deve- Abdominal segments anchylosed and rudi- 
f loped. menta 
8. Metastoma large. 8. Metastoma rudimentary." 
-I 
Anon 
T ‘Monographie des Poissons Fossiles du Vieux Grés Rouge,’ &c. 4to, p. xix. 1844. 
t ‘Contributions to British Paleontology,’ Cambridge, 8vo, 1849. 
$ Prof. James Hall, LL.D. * Natural History of New York, part vi. Paleontology, vol. iii. 4to, 1859. 
|| Archiv für die Naturkunde Liv-, Ehst- und Kurlands, erste Ser. vol. ii, 1859. 
€ “ On some new Crustacea from the Uppermost Silurian Rocks” (Salter), “ Observations on the Structure and 
Affinities of Himantopterus” (Huxley), Quart. Journ. Geol. Soc. Lond. vol. xii. 1856; “On the Anatomy and Affi- 
nities of Pterygotus” (Huxley & Salter, in Monograh 1, ‘ Memoirs of the Geological Survey of the United Kingdom,’ 
8vo, 1859). 
es ws Eurypterus lanceolatus,” Geol. Mag. vol. i. 1864. British Association Reports, 1864. Quart. Journ. ot 
the Geol. Soc. Lond. vol. xxi. (1865 
Tt Straus Dürckheim, in his atado Comparée des Arachnides, June 1829, pointed out some particulars of 
structure, the “sternum intérieur," e.g., in which Limulus resembled the spiders. This led Latreille to designate the 
Limuli * Crustacés-arachnides ” (Dictionnaire d'Histoire Nat. Art. * Entomologie, Limuli”). Other resemblances to 
Arachnides in organization will be pointed out in tlie present memoir. Whence I infer that Zimulus and the extinct 
members of the order Merostomata exemplify a more generalized condition of condylopod organization, from which 
the Arachnida, quitting the waters, may have diverged as a special branch of air-breathers. 
