8 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii. 



are laminar, with only a slight indication of a division into lobes. 

 The inner, anterior or first maxillae are typicall}^ composed of two 

 unequal lobes, the inner lobe being comparatively small, the outer lobe 

 more robust. The iEgid» have the anterior maxillae composed of only 

 a single lobe, the posterior maxilla? terminating in two lobes. The Tan- 

 aidtB also have but a single masticatory lobe to the anterior maxilUe; 

 the posterior maxillas are quite rudimentary, being simple rounded 

 lobes. The posterior maxilla? are wanting in Calatlvura Norman and 

 Stebbing; both pairs are wanting in both sexes of the Gnathiida?. In 

 the Chelif era there is a backward-directed palp attached to the anterior 

 maxillte. Exosphxroma Stebbing has a small exopod attached to the 

 first maxillae. The first maxillffi in Nalicora Moore have the outer 

 joint in the form of a strong, curved spine, the inner joint covered by 

 a cap at its tip; the second maxillte are four-jointed. Plakarthrluin 

 Chilton has both first and second maxilla?, consisting each of a single 

 lobe.« 



The mandibles are a pair of strongly calcified structures, often 

 toothed along the inner margin or consisting of a single large tooth. 

 Just below the cutting part is the molar expansion. A three-jointed 

 palp is usually present. The palp is wanting in the Tanaida?, the 

 Oniscoidea, the Idoteidne, the Arcturidje, and in the following genera: 

 Mancasellus Harger, Criiregens Chilton, Pleurogonium Sars, Macros- 

 tylis Sars, Ischnosoma Sars, Ecliinopleura Sars, Ecliinozone Sars, 

 Plakartlirhmi Chilton, and in the following species: Mkinnopsis (?) 

 australis Beddard. 



The C3miothoid», the Limnoriid^, the Armadillidiidae, the Onis- 

 cida?, the Corallanid*, the Alcironida?, the ^li]gida?, and the Bary- 

 brotidae have no molar expansion to the mandibles, as is also true of 

 the following genera: vEga Leach, Tanaopsis Sars, AnartTiura Sars, 

 and Munnopsis Sars. 



In the females of the Gnathiidae the mandibles are entirely wanting 

 and the maxillipeds reduced. In the males the mandibles are power- 

 ful structures, extending some distance in front of the head. 



The mouth parts of the Anthuridae are suctorial. In some genera 

 of this f amil}^ the molar process of the mandibles is developed into a 

 sort of semicircular saw. 



With the exception of the maxillipeds all the mouth parts are lost 

 in the males of the following genera: Paratanais Dana, Typhlotanais 

 Sars, Leptognathia Sars, and Alaotanais Norman and Stebbing. 



The oral parts in the Epicaridea are much reduced, only the mandi- 

 bles and maxillipeds being distinctly developed. 



C. THORAX. 



The thorax, pereion or mesosome, is normally composed of seven 

 free segments, articulating each with the other. Variation as to the 



" According to Pfeffer. 



