INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 523 



Fiir. 4. 



is clearly defined and extends in a gentle cnrve from the middle of tbe 

 eye to the posterior border of the embryo. This margin of the eara- 

 pax is marked ■with dendritic spots 

 of red pigment. The whole dorsal 

 portion, fnlly one-lialf the embryo, 

 is still occupied by the unabsorbed 

 portion of the yolk, (o, «,) of which 

 the lower margin , represented in the 

 figure by a dotted line, extends from 

 close above the eye in a cnrve near- 

 ly parallel with the lower margin 

 of thecarapax, but with a sharp iu- "' 

 dentation a little way behind the 

 eye. The eyes (c) are large, nearly 

 round, not entirely separated from 

 the surrounding tissues, and with a 

 central portion of black pigment. 

 The anteunulne (d) are simple, sack- 

 like appendages, arising from just beneath the eyes, with the terminal 

 portion turned backward and marked with several large dendritic spots 

 of red pigment. The antenniB (e) are but little larger than the anteu- 

 nulai and are sack-like and without articulations, but the scale and 

 flagellnm are separated and bent backvyard, the scale being represented 

 by the large and somewhat expanded lobe, and the flagellum by a 

 shorter and slender lobe which arises from near the base of the scale. 

 The mandibles, both pairs of maxiilfe, and the first and second pairs of 

 maxillipeds are not sufficiently developed to be seen without removing the 

 antenuiB and the edge of the carapax, and are onlj^ represented by several 

 small lobes, of which the anterior, apparently representing the mandi- 

 bles, are distinctly defined, while tliose that follow are much smaller, 

 indistinct, and confused. The first and second maxillipeds are each re- 

 presented by a small lobe divided at the extremity. The external max- 

 illipeds (/) are well developed and almost exactly like the posterior 

 cephalothoracic legs. Both the branches are simple and sack-like, the 

 main branch, or endognathus,t much larger and slightly longer than the 

 outer branch, or exognathus, which is quite slender. The five jiairs of 



* Embryo, some time before batching, removed from the external envelope and 

 shown in a side view enlarged twenty diameters ; a, a, dark-green yolk mass still 

 nnabsorbed; h, lateral margin of the carapax marked with many dendritic spots of red 

 pigment ; c, eye ; d, antennula ; e, antenna ; /, external maxilliped ; </, great cheliped 

 which forms the big claw of the adult ; h, outer swimming branch or exopodus of the 

 same : i, the four ambulatory legs with their exoiiodal branches ; k, intestine ; /, heart ; 

 m, bilobed tail seen edgewise. [Drawn by S. I. Smith.] 



t To prevent confusion, the terms here used are those proposed by Milne Edwards to 

 designate the different branches of the cephalothoracic appendages: endopodxs, for the 

 main branch of a leg ; exopodus, for the accessory branch, {a in iig. 7), Plate IX;) epipo- 

 dus, for the flabelliform appendage, {h ;) and endognathus, exognathus, and cplgnathns, for 

 the corresponding branches of the month organs. 



