INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 523 



Fig. 4.* 



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

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

 pax is marked Tvith dendritic spots 

 of red pigment. The whole dorsal 

 portion, fully one-half the embryo, 

 is still occupied by the unabsorbed 

 portion of the yolk, (a, a,) of which 

 the lower margin, represented in the 

 figure by a dotted line, extends from 

 close above the eye in a curve near- 

 ly parallel with the lower margin 

 of thecarapax, but with a sharp in- 

 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 antennulie {(1) 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 antennae {e) are but little larger than the auten- 

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

 flagellum are separated and bent backward, 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 maxill?e, and the first and second pairs of 

 maxillipeds are not sufficiently developed to be seen without removing the 

 antennse and the edge of the carapax, and are only represented by several 

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

 bles, are distinctly defined, while those 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 mnch larger and slightly longer than the 

 outer branch, or exoguathus, which is quite slender. The five i^airs of 



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

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

 nnabsorbed; 7), lateral margin of the carapax marked with many dendritic spots of red 

 pigment ; c, eye ; d, antennula ; e, antenna ; /, external maxilliped ; g, 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 exopodal branches ; k, intestine ; 1, 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 cei)halothoracic appendages: endopodus, for the 

 main branch of a leg ; exopodus, for the accessory branch, (a in fig. D, Plate IX ;) epipo- 

 dus, for the flabelliforra appendage, {h ;) and endognathus, exoguathus, and epignathus, for 

 the corresponding branches of the mouth organs. 



