C. Spence Bate on the Penwidea. 179 
De Haan, P. tahitensis, Heller, P. carinatus, Dana, and P. 
esculentus, Haswell, are varieties of this species (P. monodon). 
The ventral plate, which varies considerably in form in the 
females of most species, consists in this of two halves of a cir- 
cular disk, the straight side being longitudinally in the median 
line, the margins of which are curved upwards (Pl. XII. 
fig. 5, vp). ; é dis 
The petasma in the male consists of a longitudinal tube 
formed by the two plates being united together along the 
anterior surface, whereas it is open posteriorly. I have only 
had the opportunity of examining male specimens of those in 
the ‘ Challenger’ collection. 
The type specimens of the males of P. indicus and those of 
P. monodon in the collection of the Jardin des Plantes were 
too small for the full development of the parts. 
Peneus affinis, Milne-Edwards. 
(BEX Sire. G:) 
This species resembles P. ¢ndicus, from which it may readily 
be distinguished by the absence of teeth upon the inferior 
border of the rostrum, the shortness of the eyes (which scarcely 
pass the external margin of the scaphocerite), and the form of 
the dactylus on the posterior two pairs of pereiopoda, which 
are extremely slender and not sensibly flattened. 
Length about 5 inches. 
Inhabits the coast of Malabar. 
There were several specimens in the same bottle, labelled 
from Malabar; and they evidently show that Milne-Edwards 
drew up his description from a female, with which it coin- 
cides ; but among them were also several males, and these 
differed from the others in essential features; so that, had they 
not been found associated, I should have considered them 
typical forms of distinct species. 
The male has a peculiar notch or excavation on the anterior 
margin of the ischium of the fifth pair of pereiopoda (Pl. XII. 
fig. 6, 0); surmounting the notch is a slight prominence or 
tubercle. Another notch or excavation surmounted by a distal 
prominence is situated at the base on the outer margin of the 
external plate of the rhipidura (Pl. XII. fig. 6, v); in both sexes 
the telson is dorsally grooved, and terminates in a long and 
slender style-like extremity. . 
The ventral plate of the female is heart-shaped and de- 
pressed in the centre; and the petasma in the male terminates 
in a cross piece that will be better appreciated from ex- 
amination than from any description. | 
In a second bottle, labelled “ India,” is a single female 
