PROCEEDINGS OF THE NATIONAL MUSEUM. vol.64. 



FIRST ZOEA. 



The first zoea is distinguislied from later stages by the four swim- 

 ming hairs on the maxillipeds (figs. 39 and 45). 



CephalotJiorax.—Ml three carapace spines are present but they 

 are small and slender, measuring only 0.3 mm. (figs. 38 and 39). 

 The eyes are rather small. 



Appendages. — All of the cephalic appendages except the mandibles 

 are rather small. The antennules and antennae (figs. 40 and 41) 

 are especially minute and slender. 



Abdomen. — The first four segments are cylindrical but the fifth 

 segment is expanded laterally into wings that extend backward, 

 overlapping the telson. This feature is characteristic of the known 

 zoeas of the Pinnixas. The telson has the bicornuate condition so 

 often found in brachyuran larvae but is distinguished in this species 

 by the presence of a large deltoid tooth projecting medially from its 

 posterior border (fig. 47). 



MEGALOPS. 



This was reared from the last zoeal stage by Smith, but he gives 

 neither description nor figure of either. Smith was unable to rear 

 the megalops to the crab stage. 



PINNIXA SAYANA Stimpson. 



The early stages of this species have not been recorded, but the 

 last zoeal stages of a Pinnixa commonly found off the New England 

 coast have been referred to this species by Smith and Faxon. The 

 last zoea passes directly into the crab stage. The descriptions 

 given here are taken from Faxon, as are the figures. 



The carapace is armed with long frontal, dorsal, and lateral spines. The natatory- 

 feet are very short in proportion to the size of the body, the inner branch of the second 

 pair rudimentary, as usual with Brachyuran zoeae (tig. 53). The third pair of maxil- 

 lipeds and the fiAe following pairs of thoracic feet are folded under the carapace. On 

 dissecting them out from the body, they are seen to be quite perfectly formed, as 

 shown by Figure 57. The third maxillipeds (fig. 56) possess their three constituent 

 parts and a gill at their base. 



The abdomen ((ig. 62) is short, its penultimate segment expanded into two lobes, 

 which extend backward on each side of the terminal segment. The terminal segment 

 is ovate, produced posteriorly into a long spine on either side. Between the lateral 

 spines and a small median sinus are three short, finely feathered setae on each side. 



There are four pairs of simple abdominal appendages. 



There is a black pigment spot at the base of the dorsal spine, one near the base of 

 each lateral spine, and several on the abdominal somites. 



From tip of frontal spine to posterior border of carapace, 2.5 mm. From tip to tip 

 of lateral spines, 2 mm. Length of frontal spine, 1 mm. 



FIRST CRAB. 



In the first crab stage (figs. 63 and 64), which immediately follows the last zoea stage 

 just described, the carapace measures less than 1 mm. in length by 1.5 mm. in breadth. 

 The front is nearly straight, the branchial regions expanded laterally so as to form a 



