. A final report on the Crustacea of Minnesota, included in the orders Cladocera and Copepoda, together with a synopsis of the described species in North America, and keys to the known species of the more important genera . rved laterally. The eye is proportionatelysmall. The post-abdomen is long and furnished with a lateral rowof scales. The terminal claws have a single basal spine and areserrate. There is an ephippium, and the male opening is in frontof the terminal claws. Sub-genus 1.—Acroperus, Baird. Post-abdomen broad, margins parallel; anal teeth very minutelateral scales large and usur
. A final report on the Crustacea of Minnesota, included in the orders Cladocera and Copepoda, together with a synopsis of the described species in North America, and keys to the known species of the more important genera . rved laterally. The eye is proportionatelysmall. The post-abdomen is long and furnished with a lateral rowof scales. The terminal claws have a single basal spine and areserrate. There is an ephippium, and the male opening is in frontof the terminal claws. Sub-genus 1.—Acroperus, Baird. Post-abdomen broad, margins parallel; anal teeth very minutelateral scales large and usurping their place. Antennge with eightsetae (§n). Three species are described, one of which is very abund-ant in Minnesota. Sp. 1. Acroperus leiicocepliahis, Koch.(Plate E, Fig. 5. Plate I, Fig. 9.) Lynceus leucocephalus, KOCH, FISCHER. Acroperus harpw, BAIKD. Acroperus leucocephalus, SCHOEDLER, P. E. MUELLER, KURZ. Acroperus sp., HERRICK. Acroperus , , LiEviN, lilljkborg, leydig, etc., se to belong here, but I am able to add nothing to the eluci-dation of the puzzle. Body rounded above, angled behind; head moderately arched andcarinated. Lower margin of the shell pectinate, terminating in6. 82 TWELFTH ANNUAL REPORT. two teeth. The antennge are long and when reflexed the setaereach nearly to the posterior margin of the shell. The posteriorangle is not always as prominent as shown in fig. 5. Sp. a. Acroperus angustatus, Sars. (Plate I. Fig. 10.) Acroperus angustalus, V. E. MUELLER, KUKZ. This species is distinguished from the former by the head, whichis higher and very strongly arched. The dorsal contour is nearlystraight. The antennae are shorter. The form of the post-abdomenof the male is less different from that of the female than in theabove. The length of both species is about mm. The American form figured in fig. 5 of plate E differs from boththe above slightly. The head is carinated and incurved almost asin C. angustatus; the antennae fall a
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