192 Description of JVew and Interesting Animals. [Oct., 



left side, that each of these segments moved beneath the one pos- 

 terior to it, or in a direction opposite to the abdominal segments. 



The first post-abdominal segment is an exception, as its lateral 

 lobe has a narrow supernumerary' segment (not apparent in the 

 medial lobe,) attached to its anterior side near the longitudinal 

 groove. It is half the size of the normal segment to which it is 

 attached, and has the triangular projection of the abdominal seg- 

 ments, or rather it is the same part more fully developed, and se- 

 parated by a depression which, however, is continuous to the mar- 

 gin. This narrow sub-segment is fitted for sliding forward beneath 

 the tenth abdominal segment, whilst it appears to pass beneath 

 the first proper post abdominal segment. Its section is apparently 

 triangular, which would adapt it for such a movement. 



This, the first species of the genus JEonm discovered in Ame- 

 rica, seems nearly allied to Burmeister's JE. verticalis, but the eyes 

 seem to be less reniform, and the cephalic shield more nearly semi- 

 circular, and less transverse. The pygidium is dissimilar, but this 

 part was wanting in Burmeister's specimen, and replaced from a 

 detached fragment, which probably belongs to another species. 

 The processes supposed by Burmeister to arise from the posterior 

 angles of the shield, are not justified from the perfect specimen 

 now described. 



The locality of the species is Bedford county, Pennsylvania, 

 which would place it in the Pentamerus limestone, or perhaps in 

 the Trenton group. 



Apus affinis. 



Pallide fusco-olivaceus; scutum ovatum, carina dorsalis vix producta; ex- 

 cisura posterior semicircuiaris; sesmenlis caudalibus cireiter 16 pone incisu- 

 ram; incisura et cauda spinosa. Long. IJ; cauda ultra incisuram 4|; setae 

 caudaies 9^ lin. Patria: Insulae hauaienses. 



Pale brownish olive, shell ovate, slightly produced anteriorly; 

 posterior incisure semicircular, armed with a row of minute spines, 

 Wjiich are longest exteriorly; carina projecting slightly and ob- 

 tusely into the incisure: labruin subquadrate, sides converging, 

 exterior angles obtuse: antennae small, terminal articulation fusi- 

 form: mandibles eight-dentate, teeth bifid along the cutting edge, 

 and increasing in size posteriorly, points black: filamentous feet 

 four-branched, filaments decreasing anteriorly, the anterior one 

 being very small: tail with about sixteen segments projecting be- 

 yond the incisure of the shell; segments each armed with a trans- 

 verse row of small spines directed backwards: two caudal fila- 

 ments. 



The more prominent characters are as in A. longicaudatus Lee. 

 (Ann. Lycamm of New York,) the figure of which is too nearly 

 circular," the front much too abrupt, and the posterior incisure 



