494 O. W. HYMAN 



lateral hairs on the scaphognathite are now five and the posterior 

 conical portion is tripartite distally (fig. 56) . The exopodites of 

 the first and second maxillipeds become bisegmented and the 

 number of hairs at their tips is increased to six. 



The third zoea (figs. 9 and 19) has increased in length to 1.5 

 mm. The eyes are freely movable. A broad, low tubercle ap- 

 pears between the spine of the basal segment of the antenna and 

 the base of the distal segment (fig. 30) . This is the anlage of the 

 flagellum of the permanent antenna. The distal portion of the 

 first maxilla (fig. 48) has two segments and has become separated 

 from the basal portion by a joint. In the second maxilla (fig. 

 57) the scaphognathite now bears six hairs along the lateral 

 border of its anterior portion. The exopodites of the first and 

 second maxillipeds bear eight hairs. The third maxillipeds are 

 clearly distinguishable for the first time as minute buds just be- 

 hind and somewhat median to the second pair. The buds of 

 four pairs of periopods are distinguishable and those of the 

 cheliped are somewhat larger and show an identation at their 

 tips indicating the position of the chela. Blunt protuberances 

 from the ventral surfaces of the second to sixth abdominal 

 segments are the beginnings of the pleopods. On the telson (fig. 

 84) are two minute spines medial to those earlier present. 

 There is a deep groove between the sixth abdominal segment and 

 the telson, but no joint has yet developed. 



The fourth zoea (fig. 11) has increased in length to 2 mm. The 

 antennule has increased in size somewhat and a lateral hair is 

 present near its tip (fig. 24). The tubercle of the antenna is 

 greatly enlarged and the former distal segment now appears as 

 a lateral appendage (fig. 32) . The second maxilla shows several 

 changes (fig. 58). The palp is separated from the basal portion 

 by a joint and the median lobes are more pronounced. The 

 scaphognathite appears as a single plate and bears eighteen hairs 

 along its lateral border. The first and second maxillipeds have 

 nine or ten hairs at the tips of their exopodites. The bud of the 

 third maxilliped is notched at its tip, indicating a division into 

 two rami. The buds of all the periopods appear, and those of 

 the chelipeds are clearly bifurcated. The buds of the pleopods 



