37 



first joint ; third joint about half as long again as second ; thickened part of the upper flagellum 

 longer than the inner margin of second joint; lower flagellum even a little longer than the two 

 distal peduncular joints combined, in a good-sized specimen with about 24 joints. Coxre of third 

 pair of legs (fig. 20) with the inner margin concave, as the proximal inner corner is produced 

 mainly inwards as a small, rounded plate; trochanter without any tooth near the end of the 

 distal inner margin. 



The genital area is characteristic (fig. 2 0) ; inside the small plate from the proximal angle 

 of each coxa is seen a rounded protuberance, and somewhat behind these two protuberances 

 a deep, transverse, distinctly procurved furrow runs across the surface of the body separating 

 the two posterior thoracic segments, and the median part of the surface behind the furrow has 

 a conspicuous impression. 



Length a good-sized female from the Gulf of Siam 27 mm., while a very large .specimen 

 from Cheribon (Java) measures 33 mm. 



Remarks. — As this species has been taken at more localities and in much larger 

 numbers than any of the other forms, I give it the name A. vulgaris. It has affinities to 

 "■ Acetes sp." to be mentioned presently and to A. Siboga n. sp., but not to any other species. 



Acetcs sp. PI. Ill, fig. 3«. 



Stat. 47. March 8 — 12. Bay of Bima, near south fort. 55 m. Mud with patches of fine coral 

 sand. I male, 2 females. 



In a bottle with 16 specimens of both sexes of A. Sibogce and i adult female of A. 

 vulgaris I found 3 specimens, 2 among them adult, which are closely to A. vulgaris but show 

 a few differences indicating a development between A. vulgaris and A. Sibogce. 



The Male, which is 23 mm. long, agrees with A. vulgaris as to the length of the 

 joints in the antennular peduncles, and differs consequently from A. Siboga- which has third 

 peduncular joint much elongated; in the lower flagellum fifth joint of the jointed "branch" has 

 only 2 long spines, while the sixth joint has one, and the seventh 2 long spines. Coxae of 

 third pair of legs agree with those in A. Sibogcc and differ from A. vulgaris in having no 

 tooth on the distal inner angle. Genital coxse nearly as in A. Sibogcc. In the petasma the 

 processus ventralis (fig. 3«) has the outer margin more sinuate than in A. vulgaris, and the 

 capitulum differs strongly from that in A. vtilgaris^ as it is nearly twice as long as processus 

 ventralis and a little more than three times as long as broad, with the thick part distinctly 

 longer than the more slender, tapering distal part; furthermore the distal part is much longer 

 than in A. vulgaris and towards the end very slender; the armature on the front side of the 

 capitulum differs considerably from what is found in the two .species mentioned, the three hooks 

 at the proximal part of the outer margins are present, but the proximal hook is enormous and 

 the two other rather small, besides a good number of small hooks are arranged on the front 

 surface mainly in a longitudinal row from near the big hook to near the end, and the most 

 distal part has several irregularly arranged small or minute hooks. 



An adult female, which is slightly larger than the male, agrees completely with 



