THE OSTEACODA. 239 



the one central bristle about two-thirds ol: the length of the other. No basal bristles. 

 Two oi" the sense-tubes carry proximally sharp teeth. 



Malk (Mean, 201). — Shell much tis in the female of tlic same stage. Antenna i. : 

 the priueijial flagellum carries 17-20 teeth in all, which in profile look like 8-10 pairs, 

 but proximally are not quite symmetrical. There arc a few fine spines on the accessory 

 flagellum opposite the distal end of this row of teeth. Antenna ii. with two central 

 bristles, one rather longer than the other; and a small basal bristle. 



Stagk III. 



Female (Mean, 1'50). — Shell much as in Stage II. Frontal organ long, straight, 

 unscgmcuted, the future terminal joint rather thicker than the stem. Antenna i. 

 Avith hairless dorsal bristle. Antenna ii. with central bristles as in Stage II. ; at least 

 one sense-tube with a few proximal teeth. 



Male (Mean, 1-48). — Shell much as in female of the same stage. Frontal organ 

 and Antenna i. resembling those of the female at the same stage except for the absence 

 of a dorsal bristle. Antenna ii. with central bristles as in the female, with the addition 

 of one basal bristle. No hook-joint as yet developed. 



Stage IV. 



Female (Mean, 0'96). — Shell shorter for its height than in the later Stages II.-III.; 

 squarer and less triangular in outline ; the highest point of the shell is now about the 

 middle of the length instead of being behind it. Rostrum proportionately shorter. 

 Frontal organ simple, straight, unconstricted, nearly equally thick throughout its 

 length, slightly pointed. Antenna i. without dorsal bristle. Antenna ii. : longer 

 central bristle about twice the shorter one ; no teeth on sense-tubes. 



Male (Mean, I'O) agrees with the female of the same length in all the points just 

 mentioned ; distinguishable by the presence of the penis. 



Stage V. 



Female (Mean, 6G). — Shell still shorter for its height, and rostrum shorter. The 

 postero-dorsal spines nearly of the same length ; the postero-ventral prominences 

 persist. 



Male of this staii'e not observed. 



*o^ 



CONCHOECIA INERMIS, ClaUS. 



(Plate 20. figs. 122-126.) 



Only three S])ecimens were observed, d 1"5, 1*9, 2 20. Of these the two longer 

 agreed with Midler's description ; the third was a male without secondary sexual 

 characters. 



Stage ? II. 



Male (1"9). — Shell very long, the height is to the length about as 1 is to 2'7. 

 Shouldcr-ridgc lairly marked, 2)ostero-dorsal angle rounded oil', posterior border nearly 

 straight and nearly at right angles to the dorsal border; the opening of the right asym- 



