576 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



ERICHSONELLA FILIFORMIS FILIFORMIS (Say) 



Figure 103, a 



Stenosoma filiformis Say, 1818, p. 424. 



Erichsonella filiforynis (Say) Richardson, 1905, pp. 401-403, figs. 449, 450 (and 

 synonymy). 



Diagnosis. — Frontal margin below dorsal cephalic elevation with 

 elevated tubercles, one on each side of midline. Supralateral exten- 

 sion of second peraeonal somite extending outward from lateral tho- 

 racic margin. Epimeral plates wider than long, those of somites 2 to 4 

 generally (in some the tips protrude) concealed from dorsal view by 

 the lateral expansion of anterolateral somite margin; those of somites 

 5 to 7 visible in dorsal view. Midlateral pleotelson extension angulate, 

 extending far beyond pleotelson lateral border. Width (at widest 

 part) of pleotelson exceeding one-half the length. 



ERICHSONELLA FIUFORMIS ISABELENSIS, new subspecies 



Figures 103, h; 104 



TV^es.— Holotype male (U.S.N.M. No. 87482), allotype female 

 (U.S.N.M. No. 87483), and one male and one female paratype 

 (U.S.N.M. No. 89550); two male, two female paratypes. Institute of 

 Marine Science, Port Aransas, Tex.; and four female paratypes, 

 Pacific Marine Station, Dillon Beach, Calif. 



Type locality. — Ship channel. Gulf of Mexico, at Port Isabel, Tex., 

 Joel W. Hedgpeth collector, March 15, 1947. 



Measurements. — Holotype, length 11.7 mm., width at widest part 

 (second peraeon somite) 2.0 mm.; allotype, length 10.5 mm., width 

 2.3 mm. 



Diagnosis. — Frontal margin below dorsal cephalic elevation 

 smooth, lacking two raised tubercles. Supralateral extension of 

 second peraeonal somite not extending beyond lateral margin. 

 Epimeral plates longer than wide, visible in dorsal view on peraeonal 

 somites 2 to 7. Midlateral pleotelson extension reduced to a mere 

 knob. Width of pleotelson (at widest part) less than one-half the 

 length. 



The new subspecies is identical with its parent subspecies, E. j. 

 filijormis, in a number of significant respects, differing from it, as is 

 evident from the diagnosis, only in that structures present on E. f. 

 filijormis are reduced greatly in size and very slightly in configuration 

 in E. j. isabelensis. The reduced structures present an isopod that 

 superficially appears vastly different from its parent subspecies. In 

 fact, specimens of E. j. isabelensis have a great resemblance to speci- 

 mens of E. attenuaia. However, both E.j. filijormis and E.j. isabelensis 

 differ from E. attenuata in having a widely bifurcating frontal lamina 



