542 DR. J. G, DE MAN ON CRUSTACEANS [DeC. 12, 



6 Ptychognathus intermedius cle M. 1879. S ■ 



7. „ dentatus de M. 1892. 6 $ ■ 



8. „ spinicafjms Ortm. 1894. J . 



9. „ jwUenide M. 1895. d ■ 



10. „ «^»{s cle M. 1895. J. 



11. ,, 07ii/a3 Alcock 1900. c? . 



12. ,, andamanicus Alcock 1900. 5 . 



Of all these species the male is known, except of Ptych. anda- 

 manicus Alcock, which is, however, probably identical with 

 Ptych. 7'iedelii A. M.-Edw. ; of five species only has the female 

 been observed. 



According to tlieir outei- appearance and physiognomy these 

 12 species may be divided into three natural sections. The first 

 section represented by five species, viz. Ptych. dentatus, Sjiinicarjjus, 

 polleni, affinis, and onyx, of which Ptych. dentatus is the typical 

 form, is distinguished hj the following characters : — The carapace 

 is hardly broader than long, the regions usually quite distinct, as 

 also the epigastric lobes. The three teeth of the antero-lateral 

 maigins are sharp and salient. Front prominent, laminar, 

 straight, oi' nearly straight. Inner angle of the cai'pus of the 

 chelipedes produced, in the male, to form a more or less long 

 spine, except in Ptych. dentatus, in which the inner angle is acute, 

 but not spiniform. Chelfe glabrous on their outer surface, except 

 in Ptych. onyx, in which thei'e is a tuft of hair in the finger-cleft 

 and extending along the fixed finger. Ambulatory legs hairy, 

 the anterior bordei- of the merus with a subterminal spine. 



The second section is composed of Ptych. glaher, riedelii, with 

 its variety piloscc, and Ptych. andamanicus ; Ptych. riedelii may 

 be regarded as the type. The carapace of Ptych. riedelii a,nd 

 ccndamanicus is hardly bi'oader than long, that of glaher, however, 

 is distinctly broader than long. The upper surface is quite flat, 

 much depressed, the regions are not or hardly indicated, and the 

 epigastric lobes ai'e Avanting. There are two teeth behind the 

 extraorbital angle, as in the two other sections, or one {glaher) ; 

 the teeth are small, not veiy acute or distinct. Fiont prominent, 

 laminar, slightly sinuous, furrowed ti'ansvei'sely. Innei- angle of 

 the carpus of the chelipedes obtuse, rounded, or (in Ptych. anda- 

 onanicus) pronounced, tliough not spiniform. A brush of stiffish 

 hair at the tip of the fixed finger on its outer surface, except in 

 Ptych. glaher ; chelfe for the i-est glabrovis, except in Ptych. 7'iedelii 

 var. pilosa. Ambulatory legs hairy ; subterminal tooth on the 

 anterior border of the merus inconspicuous or blunt. 



The third section is represented by four species, viz. Ptych. 

 jjusillus, jnlipes, harhatus, and intermedius, of which piosillus 

 may be regarded as the type. The carapace is decidedly broader 

 than long, flat, though not much depressed. Regions more or 

 less distinct, as also the epigastric lobes. Front not prominent, 

 distinctly sinuous, and transversely ridged. The three antero- 

 lateral teeth are not very conspicuous. Inner angle of the carpus 



