92 Bulletin Vanderbilt Mdrine Museum, Vol. VI 



Material examined: Two males and one female, taken at 

 Singapore, Malay Straits, November 10, 1931. 



Technical description : This species, in many respects, re- 

 sembles Peneus semisulcatus de Man, but P. indicus possesses 

 considerable variation within the species, so much that three sub- 

 species have been established, namely, merguiensis de Man (1888) , 

 more recently set apart as a distinct species by the same au- 

 thor (1917), and variety penicillatus Woodmason, Mss., Alcock 

 (1905), and subspecies longirostris de Man (1892). The species 

 P. indicus is said to attain a length of about eight inches. The 

 "Alva" specimens are small, the male here described being only 

 about 125 millimeters long, while the largest female is about 130 

 millimeters long, both measurements being from tip of the rostrum 

 to tip of the longer uropod blade. 



The rostral carina rises slightly less than one-fourth of the 

 carapace length from the posterior margin, and is paralleled on 

 the anterior half by a lateral rostral carina, which emphasizes the 

 slight rostral crest ; this carina begins about opposite the epigas- 

 tric tooth and vanishes anteriorly approximately above the cor- 

 neal margin, or below the sixth rostral tooth. The rostrum which 

 Dr. Alcock describes from large adults as having "a manifest 

 double curve" has this double curve only faintly indicated in the 

 present specimens. In the large female of the present series, the 

 rostrum extends as far forward as the tip of the scaphocerite and 

 has the dental formula |, the epigastric spine being approxi- 

 mately in line with the hepatic spine transversely, while the first 

 and second rostral spines are above the carapace, the second spine 

 being slightly in advance of the orbital angle, while the third, 

 fourth and fifth spines are above the orbit, and the sixth or distal 

 spine is about opposite a point midway the second peduncular ar- 

 ticle of the antennulae ; the first rostral spine represents the high- 

 est point in the rostral crest, and the first, second, third and fourth 

 rostral spines are subequally spaced, the fifth spine being farther 

 in advance of the fourth than are the preceding spines, while the 

 sixth spine is about as far in advance of the fifth as the latter is 

 from the fourth spine. The rostrum is strong, the acute tip ex- 

 tending about as far forward as does the scaphocerite ; the rostral 

 spines of the ventral margin are four, the first one being above 

 the corneal margin, the second opposite the distal spine of the up- 

 per series ; the third and fourth spines of the lower series are sub- 



