51 



Gen. 6. Pachypygus, G. O. Sars, n. 



Generic Characters. Body of female very stout and compact, and pro- 

 nouncedly compressed, with the back boldly curved; that of male, as usual, 

 more slender and gradually attenuated behind. Head of moderate size and 

 rather deep. Incubatory pouch large and prominent, more or less exerted 

 at the end. Tail composed in both sexes of 4 segments, the last of which is 

 the smallest and peculiarly produced at the end both dorsally and ventrally. 

 Caudal rami claw-like- curved downwards, and tipped with a stout spine 

 accompanied by a number of smaller denticles. Anterior antennae comparatively 

 short and stout, with the number of joints somewhat reduced; those in male 

 not transformed. Posterior antennae quite smooth, terminating in a well developed 

 claw. Oral parts on the whole built on the same type as in the preceding 

 genus. The 4 anterior pairs of legs not adapted for swimming, both rami 3- 

 articulate and rather unequal, the outer one being the larger, and having the 

 setae more or less obliterated. Last pair of legs resembling in shape those in 

 Doropygus. 



Remarks. This genus is established to include the Doropygus gibber of 

 Thorell. The generic difference of this form from Doropygus was indeed 

 recognised by Giesbrecht; but I am not prepared to consent with him in 

 referring this species to the genus Notopterophorus Costa, as it differs very 

 conspicuously not only in the character from which that genus has derived 

 its name, but also in some of the structural details, as seen from the diagnoses 

 here given of the 2 genera. The genus Goniodelphys of Buchholtz seems to 

 come very near to the present genus, and should perhaps be united with it. 



14. Pachypygus gibber, (Thorell). 



(PI. XXV) 

 Doropygus gibber, Thorell, 1. c. p. 52, PI. VIII, 11. 



Specific Characters. Female. Body of a very robust and compact 

 appearance, and strongly curved ventrally, with the back boldly arched and 

 the tail more or less bent below the anterior division. Head comparatively 

 short, but rather deep, and produced in front to a short and obtuse rostral 

 prominence. The 3 succeeding segments rapidly increasing in size, the 3rd 

 being exceedingly large and deep; 1st trunkal segment only visible in its 

 dorsal part, being otherwise concealed by the adjoining segments. Incubatory 

 pouch large and prominent, with the hind extremity somewhat deflexed and 



