GULF OF MEXICO 



453 



direct influence of the subterranean river deposits. 

 The forms so far described or listed from this 

 region, though not as far as is known limited to it, 

 include the Peneidae which are of considerable 

 economic interest,^ some of the Porcellanidae, 

 Pagurids of several genera, Inachidae, though not 

 of the same species as those found in the mud 

 flats, and again, Portunids. 



The fourth group to be considered is the drift 

 invaders, chiefly from the south, brought in from 

 the south and southeast by winds, tides, and ocean 

 currents either through the Florida Straits or the 

 Yucatan Channel. This group comprises plank- 

 ton, with larval stages of decapods included, the 

 identification of which has hardly been touched; 

 also, the species that as adults, even egg bearing, 

 are domiciled on the sargassum drift and found 

 in considerable abundance whenever weather 

 conditions in the far and nearer Gulf bring seaweed 

 into the shore. In this category are to be found 

 many of the free-living of the lower crustacean 

 decapods dependent on the plant drift, larvae 

 and adults, especially of the families Portunidae, 

 Parthenopidae, Palaemonidae, and Maiidae. 



Thus, examinatioQ of our records of the decapod 

 Crustacea of the Gulf of Mexico indicates very 

 clearly large gaps in our knowledge. These gaps 

 are less evident along the northern shoi-e and the 

 Florida Keys than along the eastern part of 

 Mexico and Yucatan. However, since the physi- 

 cal environment falls into the several general 

 types as outlined, we may hope to find a fairly 

 close correlation of the fauna with environments. 

 This correlation will probably go no further than 

 to genera. 



COMPARISON OF FAUNAS 



Of all the quantitative and intensive studies 

 there are very few which give us a clue as to the 

 general sources or relationships of the Gulf decapod 

 fauna. The big question is: is this fauna largely 

 derived from the tropical forms coming into the 

 Gulf through the Florida and Yucatan Straits, 

 or, on the other hand, does it show more tem- 

 perate zone characters? Adequate answers are 

 not forthcoming from presentlj' available data, 

 but we may at least glance at the two sets of 

 fairly comparable records: (1) Schmitt's and Rath- 



' See article on shrimps by M. J. Lindner and W. W. Anderson in this 

 book, pp. 457-461. 



bun's Puerto Rican material, (2) material from the 

 northern Gulf from the Louisiana State Uni- 

 versity Laboratory at Grand Isle, Louisiana, and 

 Hedgpeth's Port Aransas, Texas, collection, 

 lumped together. Schmitt's and Rathbun's ma- 

 terial is what we may think of as typical West 

 Indian tropical. The fauna of the northern Gulf 

 will be used for comparison, since that area has 

 been worked more intensively than other regions, 

 and since drift from the tropics clearly reaches 

 that shore (sargassum inhabitants). 



Schmitt's and Rathbun's collections comprise 

 40 families, 171 genera, and 315 species. The 

 northern Gulf collections referred to above are 

 represented by 26 families, 66 genera, and 113 

 species. Of these, 21 families and 41 genera are 

 common to both groups. It may be that some lack 

 of agreement between the two sets of records is 

 due to collecting techniques. However that may 

 be, numbers show that if this comparison is to 

 have any validity the faunal records of the 

 northern Gulf need to be expanded. 



It appears from such records as are available 

 that the northern Gulf collections contain two 

 families (one genus in each), usually considered 

 temperate zone families, and not recorded from 

 Puerto Rico. Further, it appears that in those 

 families common to both collections, there are five 

 genera of the shrimp and shrimp-like crabs and 

 one genus of the Brachyura wliich occur only in 

 the northern Gulf. On the other hand, there are 

 13 families of Anomura and Macrura and 6 of 

 Brachyura from Puerto Rico which have not been 

 reported from the northern Gulf. (Whether these 

 are all truly tropical families may be questioned.) 



The materials reported here indicate a large 

 field for further taxonomic, ecological, and dis- 

 tributional studies on the decapod Crustacea of the 

 Gulf of Mexico. 



REFERENCE COLLECTIONS 



The specimens serving as a basis for com- 

 parison for future students of the Gulf decapods 

 are scattered rather widely. In this country the 

 most important are: 



The collections in the U. S. National Museum. 

 Of these may be mentioned those of Schmitt and 

 Shoemaker from the Tortugas, those of Schmitt 

 (on Walter Rathbone Bacon scholarships) from 

 two extended South American explorations, and 

 other smaller ones. 



