1893. OWEN. 25 
Twenty-one years later Professor Owen published an elaborate and 
well-illustrated memoir on that interesting, abnormal, but mis-named 
arthropod, the King-Crab (Limulus polyphemus), which is no crab, and 
has since been definitely promoted out of the class of water- 
breathing Crustacea into that of the air-breathing Arachnida and 
associated with the Spiders and Scorpions."' He detailed the mus- 
cular, nervous, digestive, and generative systems, and proposed the 
term ‘‘Cephaletron” for the anterior division of the body, and 
‘‘Thorocetron’”’ for the second ; while he declared ‘‘ the chief fossorial 
agent, as indicated by the size and disposition of the principal mus- 
cular masses, to be the cephaletral digging-shield.” While recognising 
some of the Arachnid affinities of the King-Crab as then maintained 
by Strauss-Durckeim and Latreille, Owen did not admit the necessity 
for removing the genus from the order of Merostomatous Crustaceans. 
Professor Owen’s numerous memoirs on the anatomy of the 
Brachiopoda were second only in importance to his researches on the 
Cephalopoda. In both classes he founded orders which have been 
generally accepted by biologists, and still maintain their position as 
recognised additions to zvological nomenclature and classification. 
In the article on ‘‘ Mollusca,” published in the eighth edition of the 
‘‘ Encyclopedia Britannica,” the sub-kingdom Mollusca was divided 
into the Hetevogangliata, with one nerve ganglion, and the superior 
Homogangliata of Owen. The group was compared to a tree, with 
the Cephalopoda at the summit, one of the roots appeared to be lost 
in the Turbellarian and the Trematode families of Abranchiate 
Vermes; the Brachiopoda conducted to the Bryozoa, and both, with 
the Tunicata, were considered as ‘‘mollusc-like” rather than 
molluscan. The Brachiopoda were regarded as a class equivalent in 
value to the Lamellibranchiata, and were placed between those 
acephalous molluscs and the sea-squirts, that is to say, between the 
‘‘ Acéphales testacées,” and the ‘Acéphales sans coquilles” of 
Cuvier. In 1833 the anatomy of the ‘“‘ Cuvierian genera of Brachio- 
poda,” more especially of Terebratella and Orbicula (now known as 
Discina), were described. The circulatory, muscular, and nervous 
systems of other genera were more fully investigated twenty years 
later, and the results published, accompanied by beautiful drawings 
by the author, in a ‘‘ Memoir on the Anatomy of Terebratula,” in the 
Introduction to Davidson’s classical Monograph of the ‘“ British 
Fossil Brachiopoda,” elucidating some points in the structure of 
Waldheimia and Lingula. Owen’s brachiopodal hearts are now known 
«Limulus an Arachnid,’ by E. Ray Lankester, F.R.S. Quart. Fourn. Micros. 
Sci., 1881. 
12 Waagen and F.A. Bather excepted. Mr. A. H. Foord, in his exhaustive ‘‘Cata- 
logue of the Fossil Cephalopoda in the British Museum,” 1888 (p. viii., Int., parti, 
Order Nautiloidea), states that ‘‘no evidence has as yet been brought forward that 
the fossil forms included by Owen in the Tetrabranchiata were other than four- 
gilled.” 
