138 POST-TERTIARY ENTOMOSTRACA. 



Superior margin boldly arched, deeply siiiuated in front of the middle. Seen from 

 above, compressed, oval, pointed in front and rounded off behind ; greatest width situated 

 about the middle and equal to one third of the length. The surface of the shell in recent 

 specimens appears to be very finely punctate, but a high microscopic power shows each 

 of these markings to be an exceedingly short hair. 

 Length, -4Joth of an inch. 



Distribution. Recent. — Great Britain, Ireland. 



Fossil. — Scotland : Raised beach, Oban. 



Genus 9. — Bairdia, M'Coy. 



Valves unequal in size, the left being considerably the larger, and overlapping the 

 right, both on the dorsal and ventral surfaces. Surface of the shell smooth or nearly so. 

 Carapace, as seen from the side, mostly subrhomboidal or subtriangular. Eyes wanting. 

 Antennae robust : the upper 6-jointed, first two joints large and thick, the following joints 

 very short and firmly united, but forming with the second joint a very mobile hinge ; 

 armed with numerous long setse. Lower antennae strong, 5-jointed, second joint bearing 

 on its base a bisetose tubercle, fourth joint elongated, last very short, armed with two 

 long and strong claws. Mandibles large, lower extremity slightly dilated, and armed 

 with six or seven long and strongly serrulated teeth ; palp strong, 4-jointed, bearing a 

 very small trisetose branchial appendage. One pair of jaws only, terminating in three 

 narrow subequal branches, and having a well developed branchial appendage which is 

 separated into two parts by a distinct constriction, the basal portion beset below with 

 several long slender setae, the terminal portion dilated, subovate, and fringed with large 

 ciliated setae. Three pairs of feet, all of similar structure, directed forwards and 

 protruding from the shell, 4-jointed, and terminating in a long claw ; the first pair having 

 attached to its basal joint a large ovate branchial lamina which is fringed with long 

 ciliated setae. Post-abdominal rami short but well developed, linear, bearing two 

 elongated claws, and a few setae of unequal length. The animal crawls slowly about 

 amongst the mud. 



The foregoing anatomical details are taken from G. 0. Sars' recently published 

 account^ of the genus, based on an examination of B. complanata, Brady. 



' Undersogelser over Hardangerfjordens Fauna. 1. Crustacea af G. 0. Sars (Reiseberetning), 18;i. 



