CONTRIBUTIONS TO MARINE BIONOMICS. 405 
was created for Mediterranean specimens, while Latreille’s type came 
from the west coast of France. 
2. GENERIC CHARACTERS. 
The genus Portwmnus takes its place together with Carcinus, 
Platyonichus, and Polybius in the Platyonichine, a sub-family of the 
Portunide distinguished from the Portunine by the absence of lateral 
ridges on the prelabial plate, and by the absence of a distinct accessory 
lobe to the endopodite of the first maxillipeds. 
Portumnus is distinguished from Platyonichus.by having the dactylus 
of the fifth thoracic leg of a slender lanceolate form, and the carapace 
not broader than long. In Platyonichus the dactylus is elliptical or 
broadly oval, and the carapace is broader than long. To these dis- 
tinctions I may add that in Platyonichus the interorbital margin is at 
most tridentate or quadridentate, while in Portumnus the inner angle of 
the orbit contributes a distinct accessory tooth to the frontal margin, 
rendering this margin five-toothed, as in Polybius Henslowi. 
3. SPECIFIC CHARACTERS. 
The two.species of the genus which alone are known to me are 
P. latipes (Pennant) and P. nasutus. A description of the former 
species may be found in Bell (1853) under the name Portumnus 
variegatus. The characteristic features of P. nasutus are as follows :— 
Frontal area projecting in front of the orbits in the form of a 
conspicuous triangular lobe with gently undulate lateral margins. 
The undulations mark the subdivision of the interorbital margin into 
five rounded lobules, which correspond to the five interorbital teeth 
of P. latipes. The interorbital lobe bends downwards in front. 
The carapace is relatively broader than in P. /atipes, so that the 
antero-lateral margins make a sharper angle with the median transverse 
axis. 
The orbit shows two superior fissures and one inferior fissure (pace 
Latreille and H. Milne-Edwards, who mention only one superior 
fissure), while in P. latipes the orbit is stated to be either entire 
(Bell; Leach, 1815) or provided with a single fissure above (H. Milne- 
Edwards, 1834). 
The basal joint of the second antenna is movable. 
4, CoLour. 
The colour of the carapace of Portumnus nasutus is thus described by 
Risso (1816, p. 31)—“yellowish-white, adorned with two great spots 
of coral-red ... The red spots are larger in the female than in the 
