NO. 1940. ON AL0N0P8I8 IN AMERICA— DOOLITTLE. 563 



Family CHYDOEIDAE Leach (LYNCEIDAE Baird). 



Subfamily CHYDORINA. Leaoh. 



ALONOPSIS AUREOLA, new species. 



Plates 42, 43. 



Female. — Length, 1.9 mm.; height, 0.95 mm. The form (fig. 1) is 

 longandlow; upper and lower margins are nearly parallel. The head 

 points forward, and the posterior part of the body is truncated. In 

 general proportions it resembles Alonopsis elongata Sars. The upper 

 contour is nearly straight in the body region, but slopes downward 

 more and more abruptly as it approaches the end of the rostrum. 

 The posterior margin reaches to the full height of the dorsal margin, 

 is slightly oblique and straight until it reaches the postero-ventral 

 angle. This lower posterior angle is more strictly to be regarded as 

 cut off at an angle of about 45° with the longitudinal axis of the 

 body, leaving a sinuous margin instead of the usual sharp or rounded 

 angle. Tracing the ventral margin forward, a concave portion bear- 

 ing short setae runs to a place slightly anterior to the middle of the 

 bod}', which is also the place of greatest depth; then changing direc- 

 tion slightly, another portion, also slightly concave and setigerous, 

 runs forward and joins the anterior margin without further peculiarity. 



The head (fig. 2) is low, narrow, and pointing forward; the rostrum 

 is short, and from side view is obtuse. There is a slight cervical 

 indentation. The compound eye is quite large, situated remote from 

 the end of the rostrum, and the superior margin. The ocellus, or 

 macula nigra, is one-half the diameter of the compound eye, and nearer 

 the end of the rostrum. The labrum has a large obtuse anterior lobe 

 of usual form and a slender horizontal lobe. 



The test or shell of the body possesses markings unlilce those of 

 other species of Alonopsis. Diagonally across the main portion of 

 the test, at an angle of 45°, are fine lines, 30 to the millimeter. Those 

 reaching the ventral margin anterior to the deepest point arrange 

 themselves progressively so as to be parallel with the anterior margin. 

 These lines do not encroach closely upon the cervical region. The 

 skin under the exoskeleton in some cases adds to the markings, 

 dividing the spaces between the diagonal lines into rectangular meshes. 

 Such meshes do not appear in tests from which the skin or epidermis 

 has been removed. In addition to these lines the entire test is 

 covered with fine striae which occasionally anastomose. The general 

 effect of these lines under high magnification resembles the rows of 

 papillae in the human palm, and the striae observed in Alonella excisa 

 (Fischer). These striae run, in general, 'longitudinal, parallel, in 

 side view, with the upper margin (fig. 3 B) . On the top of the head, 

 however, there is more or less of a concentration of these striae around 



