本邦産のレウコン科のクーマ類の2新種Leucon simanensis sp. nov.とL. varians sp. nov.について

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1) Leucon simanensis sp. nov., (Figs. 1, 2) Type ovigerous female specimen (length, about 5.9mm): The carapace is more than one-fifth of the total length of the animal and measures one and one-half times as long as the width, which is nearly as wide as the depth. There is a dorso-median carina with about ten teeth on the frontal lobe. The pseudorostral lobes are upturned, meeting at a distance equal to one-fourth the length of the carapace. The antennal notch is wide open. The anterior portion of the lower margin of the carapace is serrated. The length of all the free thoracic segments is one and one-half times as long as the carapace. The second segment is larger than the others, and one and one-fifth times as wide as the width of the carapace. The abdomen is much longer than the cephalothorax. The posterior produced portion of the sixth segment is broadly rounded and beset with two spines on the distal end. The first joint of the peduncle of the antennule is shorter than the second but the second joint is a little longer than the third. The main flagellum is three-jointed and about as long as the third joint of the peduncle. The accessory flagellum is minute. The basis of the third maxilliped is nearly one and four-fifths times as long as the remaining distal joints together. The basis of the first peraeopod is about nine-tenths as long as the remaining distal joints together. The carpus is longer than the ischium and merus combined. The propodus is about two-thirds as long as the carpus but longer than the dactylus. The basis of the second peraeopod is four-fifths as long as the remaining distal joints together. The carpus is much longer than the ischium and merus combined, and about twice as long as the propodus. The dactylus is about one and one-half times as long as the propodus. The third peraeopod is shorter than the fourth. The basis is nearly one and three-fourths times as long as the remaining distal joints together. The basis of the fourth is more than one and one-fourth times as long as the remaining distal joints together. The fifth is nearly four-fifths as long as the fourth and the basis is longer than the remaining distal joints together. The peduncle of the uropod is about one and one-fifth times as long as the last abdominal segment. The endopod is two-jointed and longer than the peduncle, and the first joint is about twice as long as the second. The exopod is curved outward, one and one-fifth times as long as the endopod. Remarks: The new species is very closely related to L. nasica typica (KROYER), L. n. orientalis LOMAKINA, L. acutirostris SARS and L. minor LOMAKINA. The old species may be distinguished from the new species as follows: In L. nasica typica the carapace is provided with a serrated median carina beyond the middle anterior portion and after an interval again is serrated to the hind margin. The rami of its uropod are subequal in length; the fifth abdominal segment of L. nasica orientalis has the median crest of serrations on the dorsal surface; in L. acutirostris described by Sars from the Northern European seas, the peduncle of the uropod is as long as the endopod, and the antero-lateral angle has two teeth on the inner edge; in L. acutirostris from Tatar Strait (Lomakina a 1955) the relative length of the joints of the uropod is very much like those of the new species, but the antero-lateral angle has a tooth on the inner edge; in L. minor the subequal rami of the uropod are as long as the peduncle. Occurrence: 1 ovigerous ♀ (type specimen). East part of Shinji Lake (a brackish lake, which is connected by Naka-no-umi Bay to the Japan Sea), Shimane-Ken; depth, about 6m, muddy bottom; 1960 May, 15. Coll. Mr. Taiji Kikuchi. 2) I eucon varians sp. nov., (Figs. 3, 4) Type ovigerous female specimen (length, about 4.3mm). The carapace is a little less than one-fourth of the total length of the animal and a little more than one and one-half times as long as the width, which is about as wide as the
1962-08-15

本邦産のレウコン科のクーマ類の2新種Leucon simanensis sp. nov.とL. varians sp. nov.について

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