[McMURRICH] 



NOTES ON SOME CRUSTACEAN FORMS 



49 



third. The f ureal processes are sHghtly longer than broad, their length 



to that of last abdominal segment being as five to four. Each bears 



five long plumose setae, the outermost of which is situated on the outer 



margin, some distance from the base. On 



one side indications were seen of a sixth 



shorter setae in the interval between the 



first and second long setae, counting from 

 the medial side, but no trace of this was 



seen in the furca of the other side. 



The first antennae, (fig. 5) are five 



jointed, the fifth joint being geniculate on 



the fourth. The second joint shows an 



irregular projection on its outer side and on 



the inner there is near the base a little 



tubercle bearing a short recurved spine, at 



about the middle a simple seta, and near 



the anterior extremity a group of four setae, 



two of which are feathered and two simple. 



The third joint bears a single seta on its 



inner side and the fourth two setae oh the 



outer side, and on the inner three lanceolate 



spines. The terminal joint is narrow at its 



base and broadens towards the extremity 



where it is developed into a hood-like pro- 

 cess, whose outer surface is marked by 



curved lines of fine denticulations, which extend to 

 the m^argin giving it a crenated outline. On the 

 inner surface there is a delicate film-like ridge and 

 on the outer surface a group of four setae a little 

 beyond the middle and still more distally a single 

 isolated one. 



The peculiar hood-like termination of the 

 antennales is a feature altogether unrepresented in 

 other male Monstrillas that have been described, 

 and the lanceolate spines of the penultimate joint 

 also seem to be characteristic. No branching setse, 

 such as occur on the terminal joint in M. longicornis 

 and M. anglica, were observed. 



As is usual in the Monstrillidae the remaining 

 cephalic appendages are undeveloped. The appen- 

 dages of the anterior four thoracic segments are 

 similar in form, that of the third segment being 

 shown in fig. 6. They are biramous, both the 



Fig. 4. Monstrilla canadensis. 

 The last three abdominal 

 segments and furca of the 

 male. 



Fig. 5. Monstrilla can- 

 adensis. Antenna 

 of male. 



Sec. IV, Sig. 4 



