OF WASHINGTON. 133 



the type species, there is merely a strong uniform chitinization 

 of the dorsum without any indication, in the specimens exam- 

 ined, of this chitinization being broken up into tessellated fig- 

 ures; and in my new species greeni the chitinized area is dis- 

 tinctly defined, but not especially tessellated. In the case of 

 two of the species transferred from the genus Targionia, 

 moorei Green and eucalypti Maskell, the chitinization is present 

 and a distinct indication of breaking up into a figured arrange- 

 ment is exhibited. The species casuariiicc Maskell, which is 

 brought over with the other Targionias mentioned on the 

 strength of Maskell's description and figure only, has not been 

 seen by the writer, and its present assignment is therefore open 

 to some question. Maskell says of it that it resembles eucalypti 

 in the thoracic constriction, and his figure and description would 

 indicate that it is allied to this species. In general this group 

 of species is closely allied to those assigned by the writer to 

 Targionia. 



The genus Pseudaonidia may be divided into three natural 

 groups of species. The first includes articulatus and variety 

 celastri, and lounshuryi, n. sp. The cephalothoracic constric- 

 tion is so marked a character as to justify the placing of these 

 species in the genus Pseudaonidia. The most obvious charac- 

 ter separating these from the following two groups of species 

 is the short, stout lateral spur on the posterior margin of the 

 cephalothorax. The curious pygidial spur of articulatus is 

 homologous with the third lobe of lounshuryi. 



The second group is represented by duplex Ckll. (=thecB 

 Maskell) and is characterized by very prominent, strongly 

 chitinized median lobes, by slender, hyaline lateral lobes with 

 narrow branched plates filling the intervals between the lobes, 

 and by lacking paraphyses or chitinous thickenings. The other 

 species are darutyi, trilohitiforniis, curculiginis, pceonice, and 

 greeni, n. sp., and all are very closely allied, and particularly 

 the first two, to duplex, and may perhaps be more properly con- 

 sidered as representing geographical varieties of the latter. 



The third group, of which eucalypti Maskell may be taken 

 as the typical species, has all of the lobes of the same general 

 character, the laterals merely decreasing in size (as in the 

 case of pceonice and greeni in the second group) but with plates 

 wanting or very minute and inconspicuous. This division in- 

 cludes (in addition to eucalypti) casuariiicc, clazdger, tesserata, 

 and moorei, a series of species which connects the genus Pseud- 

 aonidia with Targionia. 



Three species typical of the three groups are figured, viz., 

 articulatus (text fig. 8), and trilobitiforniis and moorei (PL 



