200 THE VOYAGE OF H.M.S. CHALLENGEU. 



Till' lu-dpoda (fig. 18) have both plates of ueaiiy equal length, ami, contrary to what 

 is the case in the typical species, are fringed with rather elongate plumose setaj. The 

 inner plate has, moreover, the inner edge, beneath the marginal setae, armed with 

 numerous unequal spines, some of which — disposed at regular intervals — are rather long. 

 The auditory apparatus within the base of this plate is much more fully developed than 

 in Anchialus typicus, the otolith being rather large and of a rounded oval form. The 

 outer plate is armed with only two spines issuing from a ledge-like projection at about 

 the middle of the exterior edge, and has the outer part liuguiform and setose all round. 



Habitat. — The three above-mentioned specimens were all collected in the same 

 locality, at the entrance of Port Philip, South Australia. The locality is given below as 

 follows : — 



Station IGl, April 1, 1874; lat. 38° 22' S.,long. 144" 36' E. ; depth, 33 fathoms; sand. 



51. Anchiahis pusillus, G. 0. Sars (PI. XXXV. figs. 19, 20). 



Promysis (?) pusilla, G. 0. Sars, Preliminary Notices on the Challenger Schizopoda, No. 54. 



Specific Characters. — Form of body rather short, with anterior division considerably 

 dilated, tail very narrow. Carapace completely covering the trunk, slightly emarginate 

 posteriorly ; frontal margin forming in the middle an obtuse angle, antero-lateral corners 

 obtusely rounded. Last caudal segment remarkably elongate. Eyes slightly expanded 

 at apex with dark jiigment. Antennular peduncle rather stout, outer Hagellum very 

 elongate. Antenna! scale less rudimentary than in the other species, denticle of outer 

 corner well defined. Legs slender, with terminal part short, triarticulate. Caudal 

 limbs in female very small, almost obsolete. Telson elongate, scarcely shorter than 

 uropods. Length, 3 mm. 



Remarks. — I have recorded this form in my Preliminary Notices as a species of 

 the genus Promysis, Dana. On closer examination I have, however, found this to be 

 incorrect, and now believe that it should more properly be referred to the genus 

 Anchialus, exhibiting, as it does, several characters in common with the latter genus, 

 not to be met with in the former. My examination of the species has not been so close 

 as could lie wished, since both the specimens in the collection were mounted in Canada 

 balsam on a glass slide, and in such a position as not to admit of examining all the parts 

 satisfactorily. 



DescripAion. — Both the specimens in the collection are females, with greatly developed 

 marsupial pouches, and thus may be assumed to have attained their full size. Not- 

 withstanding this, their length does not exceed 3 mm., and this form may accordingly 

 l)e^regarded as a true dwarf Mysidan. 



The form of the body (see PI. XXXV. fig. 19) is comparatively short, with the 

 anterior division considerably dilated, whereas the tail is exceedingly narrow. 



