376 J. Wood-Mason — Description of Lyreidiis gracilis. 



XXII. — Natural History Notes from H. M.^s Indian Marine Survey 

 Steamer ' Investigator,' Commander Alfred Carpenter, R. N., 

 Commanding, No. 8. Description of a new species of the Brachy- 

 urous Genus Lyreidus from the Depths of the Andaman Sea. — By 

 J. Wood-Mason, Esq., Superintendent of the Indian Museum, and 

 JProfessor of Comparative Anatomy and Zoology in the Medical College 

 of Bengal, Calcutta. 



LtREIDUS GRACILIS, n. Sp. 



cT . Very closely allied to L. channeri.^ Body and legs slenderer. 

 Rostrum acutely triangular with straight sides. Extraorbital and 

 antero-lateral spines absolutely as well as relatively longer. The head 

 being narrower and more produced, its sides (between the extraorbital 

 and anterior antero-lateral spines) are less deeply hollowed out, and its 

 supraorbital borders, more deeply and narrowly emarginate. Eye- 

 peduncles and corneee equal and similar, apparently of the same form 

 and proportions as in the left eye of L. channeri, the former reaching 

 to about the junction of the second with the apical third of the length 

 of the rostrum, the latter opaque yellow with the subjacent pigment 

 showing through the cuticle as a dark ring round their bases. Propodite 

 of the chelipeds armed below with three triangular spines. The mero- 

 podite bears two sharp erect spinules about the middle of the length of 

 its upper border. In all other respects much as in L. channeri. 

 The unique example obtained measures : — 



Millims. 



Length of carapace, from tip of rostrum to posterior margin, ... 233 



,, „ „ . „ to middle of a straight 



line joining bases of posterior anterolateral spines, ... 8*5 



,, ,, from same straight line to posterior margin, 15*0 



Breadth of carapace, across the parallel- sided part, ... ... 12" 7 



Breadth of head, between tips of extraorbital spines,... .,, 4*7 



Distance between tips of posterior antero-lateral spines, ... 17' 9 



Length of posterior antero-lateral spines, ... ... 5'4 



„ „ anterior „ „ „ ... ... ... 37 



„ ,, rostrum, from a straight line tangent to the bottoms of 



the supraorbital emarginations, ... ... 3*0 



,, „ extraorbital spines from the same tangent, ... 4'0 



Locality. — Off Port Blair ; 271 fathoms j green ooze ; January 

 2nd, 1888. 



* Supra, p. 206 et seqq, pi. i. 



