NO. 1729. 



ISOPOD^S FROM PERU— RICHARDSON. 



83 



A large number of specimens were collected in the oyster beds of 

 Matapalo (near Capon), Peru. They were found in wood, in holes 

 bored by them. The wood was completely honeycombed. 



The following notes were supplied by Doctor Coker: " These small 

 Crustacea are economically significant, since they enter the green 

 stems and roots of the mangroves, causing the wood to decay. The 

 falling away of these destroyed branches and roots causes the loss of 

 the many oysters attached to them. As I rarely observed the Teredo 

 in the green stems, it seems that these Crustacea are the most per- 

 nicious form and undoubtedly they prepare the way for the more 

 rapidly destructive Teredo. (A nest of young included.) 'Piojos de 

 Mangle' (Mangrove louse). Fishermen attribute to these the destruc- 

 tion of oysters that is really accomplished by the drill." 



This species differs from the other wood-boring forms of this genus 

 in the smaller number of teeth on the outer branch of the uropoda, 

 in the shape of the terminal segment, in the difference in the arrange- 

 ment of the tubercles, in the presence of a bunch of hairs on either 

 side of the terminal segment, in the trifid apical tooth of the mandi- 

 bles, in having four plumose processes on the inner lobe of the first 

 maxilla? and thirteen on the outer lobe, and in the difference in the 

 shape of the maxillipeds. 



Type-specimen.— -Cat. No. 40333, U.S.N.M. 



ORBIMORPHUS, new genus. 



Body of adult female, ovate. 



Head large, with a narrow frontal border. 



Lateral bosses present on the first four segments of the thorax. 

 Lateral to these are the epimera, which extend the entire length of 

 the lateral margin. Epimera are present on all the segments of the 

 thorax and on the first four segments of the abdomen, but are not 

 greatly developed. There are four pairs of double-branched pleo- 

 pods, and a pair of double-branched uropoda. 



The male has all the segments of the thorax distinct. Those of 

 the abdomen are fused, but at the base of the abdominal segment is 

 a notch on either side indicating a fused first segment. There are 

 no uropods or pleopods. 



Type of the genus. — Orbimorphus constrictus, new species. 



This genus is very close to Orbione Bonnier but differs in having 

 the pleural lamellae or epimera of the thorax and abdomen of the 

 female not so enormously developed. The male a also differs in 

 having the first segment of the abdomen indicated by a notch on 

 either side of the terminal segment. 



a The male of Orbione Bonnier has not been described or figured, but I hope soon to 

 give a figure of this form from a specimen of 0. penei collected recently by the Bureau 

 of Fisheries steamer Albatross. 



