. Fresh-water biology. Freshwater biology. Anus opens in depression on dorsal margin of post-abdomen; 5-7 pre-anal spines; 4-8 post-anal lateral spines in outer row. An- tennary setae usually long, some- times equaling length of valves; in some specimens they are short, apparently because of wear. Eight to ten summer eggs; true ephip- pium formed and cast off (Sars). S unknown. Color yellow or red- dish. Length, 9 . to mm. This species is /. longiremis Sars; /. halyi Brady. Not uncommon; Maine to Lake Superior and Gulf of Mexico- Probably in all regions of United States. Fig. mo. Ilyocrypt
. Fresh-water biology. Freshwater biology. Anus opens in depression on dorsal margin of post-abdomen; 5-7 pre-anal spines; 4-8 post-anal lateral spines in outer row. An- tennary setae usually long, some- times equaling length of valves; in some specimens they are short, apparently because of wear. Eight to ten summer eggs; true ephip- pium formed and cast off (Sars). S unknown. Color yellow or red- dish. Length, 9 . to mm. This species is /. longiremis Sars; /. halyi Brady. Not uncommon; Maine to Lake Superior and Gulf of Mexico- Probably in all regions of United States. Fig. mo. Ilyocryptus spinifer. 106 (103) Anus at end of post-abdomen; molting complete. Ilyocryptus acutifrons Sars 1862. MM. i. Fig. nil. Ilyocryptus acutifrons. Post-abdomen not emarginate; about 8 small spines near claws, shortest next claw; about 6 long, curved, lateral spines, about 8 marginal spines corresponding to pre-anals of other species; the proximal two directed for- ward; from distal spine of this set a series of very small marginals to anus. Antennule club- shaped, hairy. Ocellus nearer eye than inser- tion of antennules. Claws as in /. sordidus. Three to four summer eggs. $ unknown. Color reddish or yellowish. Length, 9> ca. mm. Rhode Island, Colorado 107 (100, 116) Antennary setae • ~\ basal seta of 3-jointed ramus stout 1-1-3 and stiflE Macrothrix Baird 1843 . 108 Shape oval or rotund, somewhat compressed, with dorsal crest. Head large, ordinarily not depressed; vertex evenly or abruptly rounded; rostrum short. Ventral margin of valves ordinarily with long, stout, movable spines, which project in several directions. Antennules large; lateral sense-hair near base. Antennae large; the proximal seta of 3-jointed ramus long, stiff, and spinous; the others sparsely plumose or partly spinous. Five pairs of feet. No ab- dominal process. Post-abdomen large; often bilobed. Claws small. Intestine simple, no ceca. $ with large antennules; hook on first foot. 108 (lis) Dorsal
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
