i^OG Prof. A. Alcock on a nexo Species of 



the still more primitive Dromiacea, the separation of the 

 orbital and antenuular fossae is very incomjjletej and the 

 antenna is larg^e and the elements of its peduncle are 

 nnnsually distinct ; and in Mhich also, as in many of the 

 DroDiides, the last two pairs of thoracic aj)pcn(lages are suh- 

 chcliform and reduced in size, have a strong; dorsal elevation, 

 and are often used for holding some kind of protective 

 covering — such as a valve of a Lamellibranch shell, a worm- 

 tube, a water-logged piece of drift vegetation, or some- 

 times an inert commensal — over the back, the habit indicating 

 a passive disposition and a secluded life. 



The family Dorippid?e at present embraces 10 genera and 

 perhaps 50 recent species, many of which, in conformity 

 with a well-established " law^^ applicable to primitive forms, 

 have been driven into the depths of i\\e sea. 



[I must here remark that I do not include the genus 

 Palicus, Philippi (= Ci/mopoUa, Roux), with the Durippidae, 

 although it was so placed by H. JNIilne-Edwards and is so 

 retained by Bouvier. Palicus seems tome to be an aberrant 

 Grapsoid. It may be added that this exclusion in no wav 

 affects the question here considered, since in the matter of 

 geographical distribution Palicus presents no points of 

 disagreement.] 



2. Cr^^o^'OMUS characterized, and C. andamanicvs 



DI!>TINGUISI1ED AND DIFFERENTIATED. 



Cy.monomus, a. Milne-Edwards. 



Cymonomns, A. Milne-Edwards, Bull. Miis. Conip. Zool. Harvard, viii. 

 "l, 1880, p. 2G; Milne-Edwards ct l^ouvier. Crust. I¥cap. ' Hiroii- 

 delle ' (Monaco, 1894), p. 57, and Mem. Mus. Coinp. Zool. Ilarvaid, 

 xxvii. 1, 19U2, pp. 72, 80 ; Bouvier, Bull. Soc. Philoni. Paris. (8) 

 ix. 1898, p. 59; Young, 8talk-eyed Crust. W.Indies, &c. 1900, 

 pp. 321, 323 ; Laukester, Quart. Jouru. Micr. Sci., Dec. 1903, p. 435. 



Carapace square or squarish, not concealing the anterior 

 segments of the a])domen ; with the regions faintly defined, 

 except the cardiac and postgastric, which are very distinct. 



The front forms a rostrum, and the orbito-antennal 

 border is prominent beyond the antero-lateral angles of the 

 carapace; apart from this there are no indications of orbits 

 or antennular fossie. 



The eye-stalks are either fixed or have their mobility 

 diminished, and the eyes are unpigmented and vestigial. 



The antennules are large and unconcealed. The antennal 

 peduncle is not hidden and its renal tubercle is particularly 

 prominent. 



'J'hc l)urcal cavern is large and square ; its roof is high 



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