LEPAS ANSERIFERA. 83 



times equalling, sometimes only two-thirds of, the length 

 of the scuta; in young specimens, the two occludent 

 margins form a right-angle with each other ^ in older 

 specimens they form less than a right-angle, and hence 

 the portion of valve thus bounded is unusually protube- 

 rant. Carina, within deeply concave ; exterior sides finely 

 furrowed longitudinally, generally denticulated ; valve only 

 slightly narrowed in above the fork, of which the prongs 

 diverge at an angle of 90°, or rather more, and are wider 

 than the widest upper part of the valve ; rim between the 

 prongs reflexed; the heel or external angle, just above 

 the fork, sometimes considerably prominent. I have seen 

 only a single large specimen with its carina barbed. 

 In half-grown specimens, (var. dilataia, Leach,) the carina 

 is often strongly barbed, with the upper point much acumi- 

 nated, the fork about twice as wide as the widest upper part, 

 and the prongs diverging at rather more than a right-angle. 

 In some specimens, especially very young ones, there are 

 at the base of the carina, above the fork, some strong, 

 downward-pointed, inwardly-hooked, calcareous teeth ; 

 such occur also in some specimens along the basal margins 

 of the scuta, two of these hooked teeth under the urn- 

 bones of the scuta being larger than the rest : specimens 

 conspicuously thus characterised came from the Navigator 

 Islands ; in these, I may add, the acutely triangular pri- 

 mordial valves were quite plain. 



Peduncle, generally about as long as the capitulum ; in 

 young specimens generally short. 



Filamentary Appendages, generally five, sometimes six, 

 on each side ; one is seated on the side of the prosoma, 

 and the four others placed in pairs beneath the basal 

 articulation of the first cirrus ; the lowest posterior 

 filament of the four generally is the largest. In young 

 specimens, having a capitulum only half an inch long, 

 the upper pair of the four often is not developed, or 

 is represented by mere knobs. The mouth presents 

 no distinctive characters. Cirri, with the longer ramus 

 of <the first pair almost equal to the shorter arms of the 



