SQUILLOIDEA. 



Carapax but little oblong, sides arcuate. Antennary segment broad 

 obovate, acute. Eyes large, base externally unidentate. Abdomen 

 long, posterior margin of fifth segment, and both anterior and poste- 

 rior of sixth, short spinous, last segment having a broad longitudinal 

 prominence along the middle, and the posterior margin semicircular 

 and dentate, with the teeth very numerous (more than twenty) 

 and very unequal, lateral margin straight, minutely denticulate. 

 Finger of large chela bearing nine or ten spines (the terminal in- 

 cluded) . The branches of caudal appendages subequal. 



Plate 41, fig. 1 a, outline of animal, natural size ; I, mouth ; c, 

 mandible, enlarged ; d, outline of abdomen ; e, nervous cord. 



Rio Janeiro. 



Length, nine or ten inches. The carapax is about as broad as long; 

 the front is nearly transverse, but slightly excavate either side of the 

 middle, with the middle obtuse and not more advanced than the 

 outer angles ; the posterior angles are rounded. The caudal segment 

 has the sides parallel for half an inch and small denticulate; and then 

 the margin regularly curves and is dentate ; there are, first, three 

 rounded emarginations, separated by acute or denticulated teeth, and 

 then the posterior margin, which is two-thirds of an inch long, is 

 unequally and rather crowdedly narrow dentate, with 'the interval 

 between the two median teeth rounded and a little larger than the 

 intervals near by on either side. 



The buccal area is oblong triangular. The mandibles have a slen- 

 derly dentate edge, which is situated vertically just below the poste- 

 rior margin of the buccal area, and also a long, narrow, triangular pro- 

 longation, which is acute and acutely serrulate. The palpus consists 

 of three oblong joints, subequal, the second joint a little the longest. 

 The entrance to the mouth is partly closed by a,n upper lip, which 

 hangs like a curtain in front of the mandibles. The form of the 

 nervous cord is shown in figure e, the figure is placed parallel to the 

 drawing of the animal, so that corresponding parts are in the same line. 

 The first ganglion is situated in the anterior cephalic segment, and sends 

 one pair of nerves to the eyes, and one to each pair of antennas. The 

 two main cords leaving this ganglion to pass to the next, give off each a 



155 



