564 Contributions to Invertebrate Palseontology. 



1st Section : Carapace more or less elongated, with a straight or slightly 

 arched dorsal line ; anterior end sharply rounded or pointed (rostrate) ; 

 posterior end truncate ; sides convex, smooth, or simply striate, sometimes 

 marked by a simple ocular node near the antero-dorsal margin ; no ridges or 

 other nodes. Ceratiocaris McCoy, 1849 ; Cartjncaris Salter, 1862; Hymenocans 

 Salter, 1852; Solemcaris Meek, 1872; (?) Colpocaris Meek, 1872. The last 

 somewhat questionable in character. 



2d Section : Carapace similar in form to that of Sect. 1, with the posterio- 

 basal angles produced into spines, and the surface with longitudinal ridges. 

 Dithijrocnris Scouler (^ Argas Scouler). 



3d Section : Carapace rounded at both extremities, elongate-ellij)tical or 

 elongate-ovate in form with a straight dorsal margin ; surface concentrically 

 striate, no nodes or ridges. Lingulocaris Salter, 18G6. 



4th Section : Carapace triangular, dorsal margin straight ; surface punctate or 

 reticulate, and concentrically striated (growth lines ?). Dictijocarts Salter, 1860. 



5th Section : Carapace suboval or subovate with a straight hinge-line ; 

 surface marked with longitudinal ridges or representative nodes and ridges. 

 Surface of parts smooth, punctate, or pustulose. EcUnocaris new gen. 



6th Section : Carapace broadly oval or ovate, no straight cardinal line, 

 consequently no hinge, anterior end rostrated or beaked, surface destitute of 

 nodes or ridges. Phi/socaris Salter, 1860. 



7th Section : Carapace composed of three pieces, or apparently of three ; 

 two of which are semi-circular, with the anterior end of each obliquely trun- 

 cate, forming when the two are united, an anterior triangular notch into which 

 the third or rostral plate is inserted. Surface concentrically marked by growth 

 lines; no nodes or ridges. Peltocaris Salter, 1866; Discinocaris Woodward, 

 1866 ; Apticho/jsis Barrande, 1872; Pterocaris Barrande, 1872 (not Heller, 1862). 



It will be readily seen from the above synopsis that Echinocaris 

 differs material!}' in the features of the carapace from all the other 

 genera enumerated. The features of the abdomen and caudal parts 

 are not as reliable, but are somewhat distinctive as may be seen by 

 the following table of comparison. (A mark of interrogation indi- 

 cates that the parts are unknown or only partially known.) 



Genus Ceratiocaris, abdominal segments 5 or 6, smooth, caudal spines 3. 



