126 DICHELASPIS PELLUCIDA. 



General Appearance. — The membrane of the capitulum 

 and peduncle is surprisingly thin and pellucid, so that 

 the ovarian tubes within the peduncle can be traced with 

 the greatest ease. The valves are small, the apices only 

 just crossing each other, and are composed of yellow 

 chitine, with mere traces of calcification. The capitulum 

 is pointed, oval, -15 of an inch long; the peduncle is 

 narrow, and fully twice as long as the capitulum. 



Scuta. — The two segments stand at right-angles to 

 each other ; the basal segment is linear and pointed, 

 fully half as long, but only one third as wide, as the 

 occludent segment. The point of junction of the two 

 segments is wider than the rest of the basal segment. 

 This latter segment lies some little way above the top of 

 the peduncle. The occludent segment is bluntly pointed ; 

 it is directed a little inwards from the edge of the orifice 

 towards the terga ; the apex readies up just above the 

 slightly reflexed lower point of the terga. The adductor 

 muscle is fixed under the point of junction of the two 

 segments. 



The Terga are battle axe-shaped, with the blade part 

 very prominent, smooth-edged ; behind the blade there is 

 a short upwardly-turned prominence. The lower point 

 of the handle of the axe, is bent towards the carina. The 

 terguni, measured in a straight line, equals in length 

 two thirds of the occludent segment of the scutum, the 

 handle being rather narrower than this same segment. 



The Carina is extremely narrow and much bowed ; the 

 apex reaches up only to just above the lower bent points 

 of the terga. The basal end is rectangularly inflected, and 

 stretches internally nearly across the peduncle; it consists 

 (fig. la) of a triangular disc of yellow thin membrane, 

 four or five times as wide as the upper part of the valve ; 

 the end of this disc is hollowed out ; its edges are thick- 

 ened and calcified, and hence, at first, instead of a disc, 

 this lower part of the carina appears like a wide fork ; 

 the tips of the prongs stretch just under the tips of the 

 basal segments of the scuta. 



