PORTUNUS ARCUATUS. 
Fig. 5---6. 
P. («. b.) testa convexiore lineis abbreviatis e granulis compositis, dentibus utrinque quinque, 
penultimo minore; fronte arcuato integro; manibus supra uni-dentatis; unguibus posticis 
acutis. 
Portunus arcuatus. Leach Edinb. Encycl. vii. 390. 
Trans. Linn. Soc. xi. 316. 
Fig. 5. Portunus arcuatus. 6. Maris abdomen. 
P. arcuatus differs from P. emarginatus only in the form of the anterior part of the shell, and 
may be nomore thana variety of that species. It inhabits the northern and western coasts of 
England. 
