640 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



true facets in any of the species of the genera Lecane and Monostyla; 

 some species do have facets, but the limitmg lines do not project as 

 ridges above the surface of the lorica. The majority of the species 

 having prominent ridges on the dorsal plate change their form con- 

 siderably in retraction; the species with true facets or without any 

 dorsal markings do not as a rule change much. This does not refer 

 to the virtually illoricate species, all moss-dwellers, which do not 

 assume any fixed, recurring outline in retraction. The ventral plate 

 of Lecane arcula is of nearly the same outline as the dorsal and of equal 

 width; it has rather conspicuous markings. The posterior segment 

 of the body is prominent, but nearly covered by the dorsal plate. 

 The first, immovable foot joint is nearly parallel-sided and pointed 

 posteriorly, where it reaches down over the movable second foot joint; 

 tliis is quite broad at the base and suddenly narrowed immediately 

 behind the lorica. The toes are short, rather slender, and in dorsal 

 view parallel-sided; in lateral view they are broad at the base and 

 taper rapidly. The claw is of moderate length, very slender and 

 recurved. 



Total length, 96 p.] length of lorica, including spines, 68 //; length 

 of dorsal plate, including spines, 63 jj., width, 55 n; \vidth over ante- 

 rior spines, 47 fx; length of spines, 5 fi; length of toes without claw, 

 18 in, claw, 5 fi; depth of body, 45 /x. 



Type. — Cat. No. 16573, U.S.N.M. It was taken from a stagnant 

 pool at Empire (4), where it was very abundant; it is common and 

 widely distributed on the Isthmus: Pool between Black Swamp and 

 Gatun (2); creek flowing into Camacho Reservoir (3); Rio Grande, 

 (6); Rio Trinidad, 1 mile from mouth (9), and above Agua Clara (10), 

 also at Escoval (11). 



Murray identifies tliis species with Distyla aculeata Jakubski. 

 Wliile there is no doubt a certain general similarity, it does not extend 

 to details; Jakubsld's animal is more elongate and widest in front, 

 the body is very thin and the dorsal plate smooth, the anterior spines 

 measure 14 //, while in the South American species they are only 5 // 

 long. The conclusion that the two are different species is therefore 

 unavoidable. 



LECANE COMPTA, new species. 

 Plate 20, figs. 1-3. 



Cathypna flexilis ? Murray, Journ. Royal Micr. Soc, 1913, p. 351, pi. 14, fig. 27; 

 not Distyla flexilis Gosse. 



The general form of the body is a slightly elongate oval; the ante- 

 rior margins of the dorsal and ventral plates are straight and coinci- 

 dent, the anterior spines minute. The depth of the body is moderate 

 and the entire lorica very flexible. The doreal plate is oval, trun- 

 cate in front and narrow posteriorly; the dorsal markings are 

 prominent, but in the three anterior rows only the median fields are 



