294 PROCEEDINGS OF THE NATIONAL MUSEUM vol. m 



The chaetotaxy (figs. 72-73) schematically is as follows: 



Abd. I II III IV-V VI VII VIII IX X XI XII 



*JL 12 12 12 12 b JL A 12 10 4 9 



12 16 16 16 16 16 13 



4°4 35 d 4 34 446 6 



s 4558892 



■ "i," "2," and "5." 



•> "3" Is missing. 



• "4" in the paratype, "5" In the holotype; both are probably abnormal. 



d "4" in the paratype, probably abnormal; "5" in the holotype. 



There is some difference between the holotype and one of the para- 

 types, due, no doubt, to individual variation. 



Very characteristic are several rows of small teeth on the hind margin 

 of abd. IX-XI, as follows: 



s IX: about 6 small teeth dispersed outside the outer setae. 



s X: teeth dispersed all along the hind margin. 



t IX: about 6 teeth dispersed between the inner setae. 



t X-XI : closely set teeth all along the hind margin. 



The comb of abd. VIII (fig. 74) possesses about 12 rather long teeth 

 of equal length. The upper lid of the opening of the abdominal 

 glands bears small teeth like those in Acerentomon andrei. 



The species has a small labrum (fig. 75). The maxillary palpi are 

 not distinct either in the holotype or in the paratype. 



The filamento di sostegno (fig. 76) is very small. 



The presence of a labrum, though short, and the many teeth on the 

 hindmost segments, we think, justify retaining this species in the 

 genus Acerentomon, where it is a junior synonym of A. californicum 

 (Hilton). 



Acerentulus californicus Hilton 



Acerentulus californicus Hilton, 1929, p. 132. 

 Acerentulus ba?beri californicus, Ewing, 1940, p. 550. 



In 1929 Hilton described Acerentulus californicus and gave two 

 figures. These figures, however, give only the general shape and 

 numerous setae, which are often wrongly placed and far too few to be 

 of any value in identifying the species. The description is short and 

 does not contain anything which would not fit any acerentomid. 

 The type is said to be in the Pomona College collection. 



Ewing (1940) made a new description based on a female specimen 

 sent to him by Hilton and part of some material from the type locality. 



We both independently wrote to Professor Hilton asking him 

 about his types. He replied that he had been unable to locate the 

 types, but that he had sent some specimens to the U.S. National 

 Museum, and that he did not possess any more material. Hilton's 

 types of Acerentulus americanus (Tuxen 1955, p. 125) and A. cali- 



