1894. 



PROCEEDINGS OF THE XATIOXAL JfrSEU:!. 



527 



soidal rostrum Avith median aiid marginal cariuoe; a carapace liaviug 

 live carin;e, very small spines at tlie anterior lateral anyles and angled 

 at the sides posteriorly; the lateral spines of the fifth thoracic i;eg- 

 ment curved a little forward and acute, the lateral processes of the 

 next two segments obliquely truncated and subacute; eight carime on 

 the abdominal segments, all on the last three of these segments end- 

 ing in spines; a crest and curved lines of pits on the telson, a long- 

 ventral keel, six or eight marginal spines and live subinedian, ten to 

 twelve intermediate and one to two lateral teeth; the crest and margin 

 of the telson as well as the lateral margins of the abdomen thickened 

 in the male, the thickening being greatest at the bases of the marginal 

 spines. 



General (lescripfion. — A female specimen of this si)ecies is dititicult to 

 distinguish from S. empusa. Say, but an adult male is easily reciog- 

 nized by the thickenings of the telson and sides of the abdomen, there 

 being no trace of these sexual characters in *S'. empusa. The typical 

 form exhibits other points of difference from that species, which will be 

 mentioned farther on. 



The carapace occupies about two-tenths of the total length of the 

 body and is a little longer than the telson, which is about O.IG or 0.18 

 of tlie total length. The width of the telson at 

 its base nearly e(^uals its length and the greatest 

 width of the carapace. The carapace is nar- 

 rowed in front so that the distance between the 

 anterior lateral angles only slightly ex<-eeds half 

 of the greatest wi(ith. Tlie diaiaeter of the body 

 just behind the caraj^ace is less than half the 

 greatest width of the abdomen. 



The rostrum is ovate or subtriangular and 

 faintly marked by median and marginal carinse. 



The carapace has five longitudinal carin?e, the 

 median one being bifurcated at each end, so as 

 to inclose a lozenge sliaped area, and the lateral 

 ones ending in a minute spine at each anterior 

 lateral angle. 



All segments of the hind body are provided 

 Avith submedian carina', except tlie fifth tlioracic. 

 This segment, fig. 17, nas a ]>air of acute a en- 



tral spines, and its lateral spines are acute and slightly curved for- 

 ward. In my preliminary descripti<m of this species (1891) I spoke 

 of the margins of the next two segments as bilobed, which is some- 

 what misleading, for in the first of them, while there is an anterior 

 lateral i^rocess exactly homologous to the one found in ^S. nepa, still it 

 is so small and the posterior process is so much larger, that the tejrm 

 teiuls to convey a false impression, which I wish to correct. Tiie lat- 

 eral processes of the second of these segments had better be described 

 as indented or sinuate. In both cases the posterior processes are 



Fii 



THOHACIC REGION OF 

 SQUILLA PANAMENSIS. 



