552 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.51. 



14. LEPADELLA HETEROSTYLA (Murray). 



Plate 94, figs. 9-13. 



?Metopidia rhomboides v. Hofsten, Ark. Zool., Stockholm, vol. 6, No. 1, 1909, 

 p. 70, text fig. — DiEFFENBACH, Susswasserfauna Deutschlands, pt. 14, 1912, 

 p. 190, text fig., not MetopMia rhomboides Gosse, 188G. 



Mefopidia fieterostyln Murray, Joum. Royal Micr. Soc, 1913, p. 459, pi. 19, 

 fig. 6. 



The lorica is broadly rhomboid and has a well-marked posterior 

 emargination. The edge of the lorica curves upwards from the 

 blunt lateral angles toward the anterior margin, the curvature in- 

 creasing from the angles toward the opening for the head, where it is 

 rolled back upon the dorsal plate, so that the actual outer edge does 

 not represent the morphological outer edge. The nature of this 

 peculiar structural modification is illustrated in figures 12 and 13, 

 figure 12 being a cross section through the angles of the lorica, and 

 figure 13 at the point of greatest curvature, about halfway between 

 the lateral angles and the anterior margin. The width of the lorica is 

 equal to the length. The dorsal plate is strongly convex in its median 

 section and becomes gradually recurved toward the lateral angles; 

 posteriori}^ it curves slightly upwards in the region of the lateral 

 antennae and again over the foot groove, where the upward curvature 

 is greater. The ventral plate is moderately convex and follows in 

 general the sinuations of the dorsal plate. The cross section of the 

 body consists of a roughly cylindrical median portion, produced 

 laterally as two thin wings, merging gradually with the cylindrical 

 median section; the general proportions of figure 12 are maintained, 

 with reduced dimensions, from the lateral angles to the posterior end 

 of the lorica. 



The width of the anterior margin is one-third the length of the 

 lorica. The dorsal sinus is broadly U-shaped and very shallow, its 

 depth being only one-third of the width; the ventral sinus is semi- 

 elliptic in outline and its depth equal to half the width. A stippled 

 collar is present on both the dorsal and the ventral plate. 



The foot groove is U-shaped and one-third the length of the lorica; 

 its sides gradually merge into the curved ventral plate and disappear 

 entirely at the posterior end of the body; its width is two-thirds of 

 the length. There is a semicircular emargination between two 

 rounded lobes at the posterior angle of the lorica. 



The foot is long and slender, about one-third the length of the 

 body; the terminal joint is a little more than half the length of the 

 entire foot and has posteriorly a sensory pit. The toes are as long as 

 the foot and are somewhat asymmetric; they both taper gradually 

 toward the point, but the right toe is nearly straight, while the left 

 toe curves away from it, increasing in curvature toward the point. 

 The last foot joint is twisted, so that, instead of both toes being in 



