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Stat. 47. April 8/i2. Bay of Bima, near south fort. 55 m. Mud with patches of fine coral- 

 sand. I very young female. 

 Stat. 53. April 21/22. Bay of Nangamessi, Sumba. Depth up to 36 m. Coral sand; near the 



shore mud. i male. 

 Stat. 64. May 4/5. Kambaragi-bay, Tanah Djampeah. Depth up to 32 m. Coral, coralsand. 



3 males and 4 females, all young. 

 Stat. 162. August 18. Between Loslos and Broken-islands, West coast of Salawatti. 18 m. 



Coarse and fine sand with clay and shells, i very young male and 2 females, 



one of which is as young as the male, the other of medium size. 

 Stat. 163. August 1820. Anchorage near Seget, West-entrance Selee (Galewo-)strait. 31 m. 



Sand and stone, mi.\ed with mud. i young male. 

 Stat. 164. August 20. i°42'.5 S., i30°47'.5 E. Between Misool and New Guinea. 32 m. Sand, 



small stones and shells, i young female. 

 Stat. 179. September 2/3. Kawa-bay, West coast of Ceram. 36 m. Stony bottom, i male. 

 Stat. 205. September 20. Lohio-bay, Buton-strait. 22 m. Sandy mud. i young female. 

 Stat. 213. September 26 — October 26. Saleyer-anchorage. Reef, i male. 

 Stat. 258. December 12/16. Tual-anchorage, Kei-islands. 22 m. Lithothamnion, sand and coral. 



2 very young males. 

 Stat. 273. December 23/26. Anchorage off Pulu Jedan, East coast of Aru-islands. (Pearl-banks). 



13 m. Sand and shells. 2 males and 9 females, young or of medium size. 

 Stat. 285. January 18. 8° 39.1 S., I27°4.4E. Anchorage South coast of Timor. 34 m. On the 



limit between mud and coral. Lithothamnion. i young male. 

 Stat. 296. January 24/26. io° 14' S., 124° 5.5 E. Anchorage off Noimini, South coast of Timor. 



9 — 36 m. Sandy mud. i very young male and i nearly adult female. 

 Stat. 313. February 14/16. Anchorage East of Dangar Besar, Saleh-bay. Depth up to 36 m. 



Sand, coral and mud. 5 young males and 5 young females. 

 Stat. 320. February 23. 6°5'S., ir4°7'E. Java Sea. 82 m. Fine, grey mud. i female. 



The examination of these numerous specimens, though mostly young or of medium size, 

 proved that Penacopsis stridtilans (W.-Mas.) is a very variable species. At first, indeed, 

 these specimens did appear to me to belong to Uvo different species, but the existence of 

 several transitional forms led me to the conclusion that all ought to be referred to one and the 

 same species. The variability bears upon the toothing of the rostrum, the more or less distinct 

 development of the branchiostegal spine, the form of the stridulating-organ and the number of 

 its ridges, the shape of the carina on the 3"^ abdominal tergum, of the thelycum and of the 

 thoracic legs, as also the length of the telson. 



The female from Stat. 320 is adult, 88 mm. long. The rostrum, slightly curved upward 

 on its distal half and reaching to the end of 2'"' antennular article, is armed with 7 teeth in 

 addition to the small, epigastric tooth. Branchiostegal spine smaller than in Alcock's figure 14^. 

 .Stridulating-organ rather broad, consisting of 10 or 11 ridges. Branchial region defined, besides 

 by a shallow groove below the hepatic spine, also by a sinuous furrow that from the hepatic 

 spine runs nearly to the posterior border of the carapace. This sinuous furrow, that runs as in 

 Pen. coniger (Alcock, I.e. PL IV, fig. 12), should not occur in the typical Pen. stridiilans. The 

 thelycum shows a different form from that of the typical siriduians, as figured by Alcock 

 (I.e., fig. 14^'). The anterior plate between the legs of the 4'h pair is longer in proportion 

 to its width and appears therefore less transverse; the posterior transverse lamina is distinctly 

 divided into three lobes; the transverse bar between both, finally, differs by the lateral walls 

 that are longer, cjuite parallel with one another and making right angles with 



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