264 ZOOGEOGRAPHY 



TABLE 4. {Continued) 



Macrostylis setifer Menzies, 1962a. North of Puerto Rico Trench, 5477- 



5494 m 

 Macrostylis vemae Menzies, 1962a. North of Puerto Rico Trench, 5410- 

 5684 m 

 Family Mesosignidae 



Mesosignum kohleri Menzies, 1962a. Colombia abyssal plain, 2868-4076 m 

 Family Nannoniscidae 



Nannoniscus camayae Menzies, 1962a. Off Panama, 1714 m 



SUBORDER GNATHIIDEA 



Family Gnathiidae 



Akidognathia poteriophora Monod, 1926. OfTU. S. Virgin Islands, 914 m. 



SUBORDER VALVIFERA 



Family Arcturidae 



Antarcturus annaoides Menzies, 1956b. South of Jamaica, 1244 m 

 Arcturus caribbaeus Richardson, 1901. OffAves Island, 1360 m 

 Arcturus purpureas Beddard, 1886. Off Leeward Islands, 900 m 



Note: Records from deep water around Bermuda are not included. 



great area of mixed-salinity waters resulting from the outflow of the Orinoco, 

 Amazon, Tocantins, and Parnaiba rivers form an effective barrier to the 

 movement of shallow-water isopod species. 



3. Species having an amphi-Panamic distribution — 7 species, 4.2% [8, 

 3.7%] (Table 5). In spite of the history of immergence and emergence of the 

 Isthmus of Panama, this very small amphi-Panamic component in the Carib- 

 bean isopod fauna suggests that most of this fauna has evolved since the last 

 emergence of the late Pliocene. Given the limited mobility of most isopod 

 species, the Panama Canal seems to have played a minimal role in contribut- 

 ing to this component. 



4. Species occurring outside of the western Atlantic (but excluding the 

 amphi-Panamic species) — 3 species, 1.8% [7, 3.2%]. 



5. The role of the Gulf of Mexico isopod fauna (see Clark and Robertson, 

 1982) in the composition of the Caribbean/Bahamian is complex and diffi- 

 cult to analyze. One hundred and thirteen species of shallow-water isopods 

 have been recorded from the Gulf of Mexico (Table 6). This number would 

 indicate that many species remain to be recorded in this region. Of these 1 13 

 species, 61 (54%) have also been reported from the Caribbean region. It is 

 therefore possible that there exists a true Gulf of Mexico fauna, whose evolu- 

 tion was perhaps spurred by the relative isolation and reduction of the Gulf 



