10 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



crypta colombiana Garth, and a Parthenope (Pseudolambrus) species 

 herein described, now bring the total representation for the family from 

 the eastern Pacific to nine genera and 16 species. In point of abundance 

 Heterocrypta occidentalis (Dana) has proven to be a dominant species 

 on sandy bottom within its range, as a glance at the table of material 

 examined for this species will demonstrate. 



The Hymenosomidae, according to Alcock (1900), are "small ma- 

 rine and estuarine [crabs] having a curious superficial resemblance to 

 some of the Oxyrhynch crabs of the Inachine subfamily." Their sys- 

 tematic position is still somewhat uncertain. There are authors who, fol- 

 lowing Milne Edwards (1837, p. 28), have placed them among the 

 Catometopa near the Pinnotheridae, or near the Mictyridae, as did 

 Alcock (1900, p. 291). Others, notably Ortmann (1893, p. 31) and 

 Rathbun (1925, p. 561), have followed De Haan (1839, p. 75) in 

 placing them in the Oxyrhyncha near the Majidae. It is the latter course 

 that is adopted here, albeit without prejudice to possible future phylo- 

 genetic studies. Only one American species is involved, the remaining 

 members of the family being Australian or Asiatic. 



Sexual Dimorphism 



The dissimilarity of the sexes among the Majidae has led to a 

 number of instances in which male and female of the same species were 

 originally described as two species and as often as not placed in different 

 genera. Classic examples are Oregonia gracilis (male) and O. hirta 

 (female) of Dana, combined by Smith ( 1880) , Erileptus spinosus (male) 

 and Anasimus rostratus (female) of Rathbun, combined by Schmitt 

 (1921), Libinia smithi Miers (male) and L. hahni A. Milne Edwards 

 (female), combined as Libidoclaea smithi by Rathbun (1925), and, in 

 all probability, Temnonotus granulosus (female) and T. simplex (male) 

 of A. Milne Edwards, as suggested by Rathbun (1925, p. 343). 



In the present volume Epialtus minimus (male) of Lockington and 

 E. crenulatus (female) of Rathbun are combined, as are her Euprog- 

 natha bifida (male) and Batrachonotus nicholsi (female), the former 

 name in each case taking precedence. Her Epialtus peruvianus, 1923a 

 (male), and Eupleurodon peruvianus, 1924a (female), are combined as 

 Eupleurodon peruvianus, 1923. The importance of such consolidation is 

 best understood when one considers that, apart from these now unmasked 

 females, the genera Anasimus and Batrachonotus are unrepresented in 

 the Pacific. 



