Mr. C. Spence Bate on Nannastacus binoculoides. 87 



the posterior portion of the carapace do not extend so far ante- 

 riorly as the rostrum, and do not meet in front. The pereion 

 has four somites exposed posteriorly to the carapace. The eyes 

 are sessile, and situated one on each side. The pereiopoda have 

 the seven joints normally developed, and support a secondary 

 appendage. The four last somites of the pleon, with the telson, 

 are wanting ; therefore the form of the posterior pair of pleopoda 

 and of the telson are not known. 



Nannastacus binoculoides. PI. I. fig. 4. 



The anterior portion of the carapace is centrally elevated in 

 the stomachal region, and crested by two parallel longitudinal 

 rows of small beadlike tubercles. It is depressed centrally and 

 elevated anteriorly and laterally, forming three conspicuous lobes: 

 the anterior is an obtuse rostrum, rounded above, and covered 

 with minute tubercles; the lateral lobes correspond with and 

 support the organs of vision. The posterior division of the cara- 

 pace is anteriorly produced laterally and inferiorly beyond the 

 eyes. The infero-lateral margin not only ascends, but meets the 

 anterior margin of the lateral processes at a right angle, the 

 point of meeting being anteriorly produced into a sharp denticle. 

 The posterior margin of the carapace is thickened into a strong 

 and elevated ridge, which is dorsally crested with strong tuber- 

 cles. The first two exposed somites of the pereion are very 

 short, and are crested dorsally with fine tubercles. The third 

 and fourth somites are longer than the first two 5 bnt they are 

 also narrower, and have the dorsal tubercles more prominent 

 than those on the preceding. Posterior to these are the only 

 three somites of the pleon that are known ; these are scarcely 

 longer than broad, and are dorsally furnished with crests of 

 small tubercles. 



The characters of the posterior pairs of pleopoda and telson 

 are unknown. 



The eyes are small, sessile, and situated one on the centre of 

 a lobe on each side of the head. The antennas and organs of the 

 mouth I have not been able to determine, from a reluctance to 

 dissect a unique specimen. 



The second pair of gnathopoda assimilate closely in form to 

 those of the first pair of pereiopoda in the normal Diastylis, and 

 extend anteriorly in front of the carapace to some distance. 

 The first four pairs of pereiopoda have the coxse small, and 

 armed with tubercles ; the bases are long and broad, and the 

 remaining joints developed upon the type of true Macrurous 

 Decapoda, terminating in sharp well-developed dactyli. 



The last pair of pereiopoda differ from the preceding in having 

 the coxa very reduced in size, and the basis narrowed to slen- 

 der proportions. A secondary appendage consists of a strong 



