

CALASTACUS. 



105 



} 



CALASTACUS Fas. 



Bull. Mus. Comp. ZooL, XXIV. 194, 1893. 



Cepbalo-thorax laterally compressed. Abdomen long, enlarged in the 

 middle, narrowed at each extremity, pleura) l3road and rounded. Rostrum 

 lon.^ pointed; eyes rudimentary, subglobose, without pigment and un- 

 facltcd. Second antenna) on a horizontal line with the first antenna); the 

 second segment is armed with a long external spine (styloccrite), and a still 

 longer articulated style-shaped scale (scaphocerite). Third maxilhpeds pedi- 

 form. First and second pairs of legs chelate. First abdominal appendages 

 of the male modified to serve as sexual organs (gonopods). Outer branch 

 of the swimmerets divided near the posterior margin by a diagonal suture. 

 Telson long, quadrangular. Gills composed of a central stem, bearing two 

 rows of filaments. The number and arrangement of the gills are shown by 

 the following formula : 



Somites 

 Epipods 

 PodobrancliiiB 

 Arthrobranchise 



Plcurobraiiohia? 



VIII.* 



1 





 

 



IX 



1 

 1 



2 

 



X. 



1 

 1 



2 

 



XI. 



1 

 1 



2 

 



XII 



1 

 1 

 2 

 



XIII, 



1 

 

 2 







XIV, 





 

 

 



(*5) 



4 



10 







14 + (6) 



This genus is closely related to Calocans Bell In both genera the con- 

 dition of the aborted eyes is the same; the two anterior pairs of legs alone are 

 chelate • the first abdominal segment bears, in the male, a pair of specialized 

 sexual appendages, and the outer plate of the sixth pair of abdominal ap- 

 pendages is divided near the end by a diagonal suture. I have not seen 

 femakts of either genus, nor have I examined the gill arrangement of Calo- 

 cans, there being but two specimens of Calocans macandrcm in this Museum.f 



The presence of a long styloid scaphocerite appended to the peduncle of 



* Tho somite wliicli bears llie second pair of maxillipcds is here reckoned as tlie cigUtli. 

 t According to Ortmann (Zoolog. Jalirb., Abtli. f. Syst., YI. 50, 1891) tlie brancliial formula for 

 caris niacandrefS is as follows : 



Cah 



Somites 



Epipods 

 Podobrancliise 



Arthrobrancliise 



Plcurobi-ancliia) 



VIII. 



IX. 



X. 



XI, 



XII. 



XTII. 



XIV. 











1 



1 



1 



1 







1 



1 



1 



1 



1 











1 



3 



3 



2 



2 



2 



































(4) 



5 



11 

 



10 + (4) 



14 



-VI 



