DECAPOD CRUSTACEANS OF THE BEAUFORT, N. C, REGION. 389 



more slender. Thelycum consisting of an anterior thin plate bifurcate anteriorly and a posterior 

 shorter emarginate plate which are situated on the sternum between the last three pairs of legs. Telson 

 about as long as sixth abdominal segment, thickened and convex above, its margins sinuate and con- 

 verging to a narrow, rounded tip. Both blades of uropods with their distal third curved outward. Plu- 

 mose hairs, mostly long and slender, are present in abundance along the front of the carapace, the 

 margins of the telson and uropods and the superior surface of most of the legs. 



Length, 27 mm.; carapace, 8.5 mm.; antenna, 16 mm. 



Color, a translucent white, flushed with pink and yellow on the tail fin and legs. 



A single specimen of this shrimp, an egg-laden female, was taken in the otter trawl in about 2 

 fathoms of water o5 the ocean beach of Bogue Bank about a mile west of Fort Macon on July 30, 1914. It 

 was taken to the laboratory and kept alive for several days in a small aquarium where its behavior, as 

 well as its appearance, strongly suggested some thalassinid. 



The specimen is of unusual interest as it is the second one of the species and genus to be recorded from 

 the Atlantic coast of the United States, and it throws a good deal of light on a very inadequately known 

 group of crustaceans. There can be no reasonable doubt that it is correctly identified as O. alphcerostris 

 since it agrees in all essential respects with Kingsley's description of that species, and the locality at 

 which it was collected is reasonably near the type locality. Kingsley's specimen was collected by 

 Prof. Webster on the ocean side of Northampton County, Va. , and is now in the collection of the United 

 States National Museum. Unfortunately, however, it and several other specimens which would be of 

 value in the present connection have been sent to Dr. H. Coutifere, 

 of the Paris Museum, for study and no direct comparison can be 

 made. Kingsley stated that it was in bad condition, and this fact 

 may account for some of the discrepancies between his description 

 and figure and the specimen in hand. 



At the present time four species of Ogyris are known : O. orientalis 

 Stimpson <» from the China Sea and southern Japan, O. alpharostris 

 Kingsley from the coasts of Virginia and North Carolina, O. occidentalis 

 Ortmann * from the mouth of the Tocantins River and from south- 

 western Louisiana, and O. sibogm De Man'' from the Sulu Sea and 

 Saleh Bay in the Dutch East Indies. 



It has been assumed that the triarticulate carpus of the second ^°- "--Of^" alplusrostris. stema 



- , , „ ■ J }• J /^ jj.1 J ■ J' i- • 1. ii_ J. of last three thoracic segments show- 



pair of legs of O. ortentalis and O. alphcsrostris distmguishes them at ■ ^^^ thelycum x? 



once from O. occidentalis and O. sibogcE in which this part is described 



as being quadriarticulate. There is little doubt, however, that in the use of the term triarticulate both 

 Stimpson and Kingsley referred to the articulations while Ortmann and De Man referred to the articles 

 of the carpus, and that an examination of the specimens will show that throughout the genus the carpus 

 is composed of four articles. It will also probably be found that in all four species there is a small rostrum 

 and that the telson is thick, uneven above, and with sinuous sides. Assuming these characters to be 

 present, O. alph<Brostris is distinguished from the others by its smooth, noncarinate carapace, O. occi- 

 dentalis may be known by the presence of seven to nine teeth, and O. orientalis and O. sibogcE by the 

 presence of four or five teeth on the dorsal carina of the carapace. The last two species may, per- 

 haps, be distinguished from each other by the larger size of the rostrum and the more strongly devel- 

 oped protuberance on the lateral margin of the telson in O. sibogce, but one is inclined to believe that 

 they may prove to be identical. 



Whether a thelycum is present in the female of any other species of Ogyris than the one here described 

 can not be ascertained. Such a structure is not mentioned in any other description, but that fact does 

 not prove its absence. The specimens previously described have been, in nearly every instance, very 

 small or more or less mutilated and imder such conditions the thelycum might easily have been overlooked 

 or mistaken for something else. A thelycum is found in the shrimps of the family Peneidae and a some- 

 what similar sperm receptacle is characteristic of the crawfishes of the family Astacidse, but its occur- 

 rence and unusual development in Ogyris alphcerostris is most unexpected. 



" Proc. Acad. Nat. Sd. Phil, .xn, 36, i860. 



6 Ergibnisse dcr Plankton-Exped. der Huraboldt-Stiftung. Dekapoden and Schizopoden, 1893. 



cSiboga Expedition, Decapoda, monograph xxxixa. 



