612 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 113 
Pomagnathus corallinus Chace 
Pomagnathus corallinus Chace, 1937, p. 124, fig. 5—Schmitt, 1939, p. 12. 
MatertaAu: Northeast shore, rocks south of landing place; July 21, 
1938; Sta. 9; W. L. Schmitt; 2 males. 
MEASUREMENTS: Carapace lengths to base of rostrum, 2.7 and 3.1 
mm. 
Remarks: These are apparently the only known specimens of this 
genus and species, aside from the type. Except for their smaller size, 
they agree in nearly all respects with the ovigerous female type from 
Baja California. The inner antennular flagella, which were broken in 
the type, are fully twice as long as the outer flagella. The appendix 
masculina on the second pleopods is about half as long as the appendix 
interna in the smaller specimen, about two-thirds as long in the larger. 
In the form of the front, the proportions of the antennules and anten- 
nae, the form of the chelipeds, and the expanded third maxillipeds, 
Pomagnathus bears an obvious resemblance to Metalpheus, which was 
proposed by Coutiére for certain species of Alpheus similar to A. 
clippertom. Only a thorough study of the entire family can determine 
whether the absence of pereiopodal epipods in Pomagnathus and their 
presence in the superficially similar species of Alpheus is of sufficient 
importance to justify the retention of the genus. 
DisrriputTion: Known otherwise only from Arena Bank, Baja 
California. 
Synalpheus biunguiculatus (Stimpson) 
Alpheus biunguiculatus Stimpson, 1860, p. 31. 
Synalpheus biunguiculatus Banner, 1953, p. 32, fig. 9. 
Mareriau: Northeast shore, rocks south of landing place; July 21, 
1938; Sta. 9; W. L. Schmitt; 2 ovigerous females.—Northeast transect, 
36 feet; August 27, 1958; Chess and Hambly; 1 ovigerous female.— 
Northeast side, 45 feet; August 28, 1958; Limbaugh, Chess, and 
Hambly; 1 specimen.—From coral in 20-40 feet; August 1958; 
Allison and Limbaugh; 1 ovigerous female.—Northeast side, 50-60 
feet; September 20, 1958; C. Limbaugh; 1 specimen. 
MEASUREMENTS: Carapace lengths to base of rostrum, 3.1-4.7 mm.; 
of ovigerous females, 3.3-4.7 mm. 
Remarks: The two specimens without eggs are probably males, as 
indicated by the form of the abdominal pleura and pleopods; each has 
a carapace length of 3.1mm. The specimen with a carapace length of 
4.7 mm. is referred to this species with some doubt, for it lacks all of 
the pereiopods; the largest specimen that is identified with certainty 
has a carapace length of only 3.9 mm. 
There seems to be considerable variation in this species as regards 
the breadth of the rostrum, the proportions of the segments of the 
antennular peduncle, the length of the stylocerite, the length of the 
