NATURAL SCIENCES OF PHILADELPHIA. 133 



surface obscurely tuberculose, nor is the inferior portion smooth. 

 The carapax in the female is nearly plane, and the lateral margins 

 of the branchial region are not tuberculose. 



LEUCOSOIDEA. 

 Calappa galloides, Stimpson. Arm. Lye. Nat. Hist. New York. Vol. 

 VII. p. 71. 



ANOMOURA. 



Dkojiia lator, H. Milne-Edwards. Hist. Nat. des Crust., Vol. II. p. 174. 



Petrolistiies nodostjs, Nov. sp. 



The carapax is broadly ovate, about as broad as long. It is 

 nearly plane from side to side, and convex from behind forward. 

 The anterior portion is nodulated; the nodules are arranged in a 

 semicircular manner transversely across the dorsum from one 

 hepatic region to the other. There are two nodules, larger than 

 the others, placed in the centre behind and between the orbits. 

 The posterior portion of the carapax is indistinctly imbricated. 

 The front is prominent and deeply tridentated. The middle tooth 

 is the largest and triangular in shape, and very slightly more 

 prominent than the lateral ones. The lateral teeth are broad; 

 their outer margin is convex and the inner is concave; their apices 

 are directed inward. A shallow groove is in the middle of the front ; 

 and there is also a groove on each side running down into the 

 lateral teeth. The superior margin of the orbit is inflated and 

 everted. The external angle is acute, but not prominent. The 

 eyes are large. The peduncles of the antennae are knobby; the 

 first article presents an obtuse tooth on its anterior margin. 



The right cheliped was missing. The left is large, compressed, 

 imbricated on the superior surface, and smooth on the inferior. 

 The hand is as long as the carapax ; the width is greater at its 

 junction with the dactylus than where it joins the carpus. The 

 posterior margin is covered with a dense pubescence. The dac- 

 tylus and propodus closely approximate, and their approximated 

 borders are finely denticulated. Their extremities are hooked. 

 The dactylus presents a slight groove on its superior surface. The 

 carpus is shorter than the hand. The anterior margin is armed 

 with four large, serrated, and imbricated teeth; the two middle 

 ones are the largest, and are united at their bases ; the external 

 tooth is smallest. The superior edge of the distal extremity of 

 the carpus is dilated. There is a small tooth at the external angle ; 



