59.53,842(72.2) 



Article XX.— THE BRACHYURAN CRABS COLLECTED BY 



THE U. S. FISHERIES STEAMER 'ALBATROSS' IN 1911, 



CHIEFLY ON THE WEST COAST OF MEXICO 1 



By Mary J. Rathbun 

 Plates XXVI to XXXVI 



The number of species in this list is 56, which by no means represents 

 the existing fauna of the region. There are, however, a number of new 

 and rare species which add value to the collection. A new species of 

 Sesarma has already been described from Magdalena Bay, and the males 

 of two unknown species of Pinnotheres are described below; these may 

 later on be linked up with the females of the species, which are perhaps 

 already described. The differences in shape and general appearance 

 between males and females of this genus are usually too great for one to 

 identify both sexes of a species unless they are found associated. A 

 series of Pilumnus from Lower California enables the author to estab- 

 lish the presence of two closely allied species with continuous ranges 

 which overlap at Magdalena Bay. The ranges of various species are 

 extended, including those of Lophopanopeus heathii, Panopeus bradleyi 

 and Collodes tumidus. Also noteworthy is the. presence in the collection 

 of a well-developed specimen of Pliosoma parvifrons, a species of rare 

 occurrence. 



A considerable collection of young stages, chiefly crab megalopa, 

 was obtained. It is impossible to identify all of them with certainty, 

 as our knowledge of the development of these creatures is still very 

 limited. It has been thought best to publish drawings of the different 

 forms, that future students who contrive to raise the young from the eggs 

 may be able to classify them. The drawings of larvae were made by 

 Dr. Charles J. Fish, of the Bureau of Fisheries, who is making an inten- 

 sive study of the plankton of the Woods Hole region. He has sug- 

 gested the generic position of several of the Lower Californian larvae 

 which are akin to others on the Atlantic side. 



Dromiidje 

 Dromidia larraburei Rathbun 



Dromidia sarraburei (by error) Rathbun, 1910, Proc. U. S. Nat. Mus., XXXVIII, 

 October 20, p. 553, PL xlviii, fig. 4. 



'Scientific Results of the Expedition to the Gulf of California in charge of Dr. C. H. Townsend, by 

 the D. S. Fisheries Steamship 'Albatross' in 1911; Commander G. H. Burrage, U. S. N., commanding. 

 XIII. Published by permission of the U. S. Commissioner of Fisheries. 



