REPORT ON THE CRUSTACEA MACRURA. 249 



the dorsal surface longitudinally grooved in the median line, and the lateral margins 

 fringed with cilia. 



Length, 127 mm. (5 in.) male 



Habitat.— Station 203, October 31, 1874; lat. 11° 6' N., long. 123° 9' E.; depth, 

 20 fathoms ; bottom, mud. One specimen; trawled. 



The specimen in the Challenger collection appears to correspond more closely with 

 the description that Milne-Edwards has given of the species than does the typical 

 specimen preserved in the Museum of the Jardin des Plantes, of which I have given a 

 figure in the Ann. and Mag. Nat. Hist, for September 1881. In the type the rostrum 

 is slightly elevated at the extremity, and the crest at the base is not remarkable, whereas 

 in our specimen the rostrum continues in a horizontal line to the apex, and the crest 

 is strongly marked at the base. Our specimen is a male, while that of Milne-Edwards 

 is a female. The Challenger specimen has eight teeth on the dorsal margin, of which 

 the most anterior is small, and there are four on the lower margin. The rostral carina 

 gradually decreases to the posterior margin of the carapace. 



The posterior three somites of the pleon are compressed, and the last two are cariuated. 



In our specimen the sixth somite terminates in a small tooth, but in Milne-Edwards' 

 specimen the tooth is somewhat larger. 



The ophthalmus is moderately large and stands on a long ophthalmopod, of which 

 the first joint projects laterally. The first pair of antennae has slender flagella, the longer 

 of which is slightly longer than the peduncle, which is subequal with the rostrum. The 

 prosartema reaches beyond the ophthalmopod, and the stylocerite does not extend so 

 far as the extremity of the eye. The second pair of antennae has a nagellum that 

 is long, slender, and twice the length of the animal, and the scapbocerite reaches a 

 little beyond the extremity of the rostrum. Milne-Edwards remarks that the chela? 

 of the three anterior pairs of pereiopoda are long and slender, but they do not 

 appear to be remarkably so beyond those of other species. In our specimen the 

 petasma corresponds with the same organ in Penseus monodon. And in all other respects 

 I can find no definite separating feature beyond the existence of one little tooth at the 

 anterior extremity of the rostrum, and another on the inferior margin. In the larger 

 specimen, that is, in Penseus monodon, the first pair of antennae has the outer flagellum 

 much thicker at the base, but this is only a feature characteristic of a matured male. 

 The longitudinal grooves on the inner and outer plates of the rhipidura are similar; 

 and the telson and the detads of the structure throughout appear to be identical. 



Our only specimen that corresponds with Milne-Edwards' description of Penseus 

 i 'ad icus is a male, and was taken, associated with two large females of Penseus monodon, 

 among the Phdippine Islands. 



The ventral plate or thelycum in the female, from which Milne-Edwards drew his 



(ZOOL. CHALL. EXP. PART LIT. 1886.) Fff 32 



