Exosphaeroma alba 229 



Exosphaeroma Stebbing, 1900 



DIAGNOSIS Maxillipedal palp articles 2-4 produced medially into lobes. 

 Pereonites 6 and 7 dorsally unarmed. Pleopod 3, exopod biarticulate. 6: 

 Penes short, separate. Copulatory stylet of pleopod 2 elongate, slender. 

 Pleotelson lacking strong apical notch. 9: Mouthparts not metamorphosed. 

 Broodpouch of three pairs of oostegites on pereonites 2-4; oostegites short, 

 not reaching midline. Brood held in four pairs of internal pouches. 



Key to species of Exosphaeroma 



1. Pleotelson with posterior margin entire, evenly convex 2 



Pleotelson with posterior margin faintly notched or trilobed 3 



2. Frontal lamina with length less than 1.5 times greatest width diminuta 

 Frontal lamina with length almost two times greatest width 



productatelson 



3. Pleotelson with posterior margin faintly trilobed, and with three low 



rounded tubercles anteriorly yucatanum 



Pleotelson with posterior margin faintly notched 4 



4. Pleotelson posteriorly broadly notched; two rounded submedian 



tubercles on inflated midregion antillense 



Pleotelson with faint narrow notch posteriorly; lacking dorsal tubercles 

 alba 



Exosphaeroma alba Menzies and Glynn, 1968 

 Figure lOOA-C 



DIAGNOSIS 6 2.0 mm, 9 2.3 mm. Frontal lamina anteriorly broadly 

 rounded, basally slightly wider than midlength. Pleotelson similar in S and 

 9 ; anterodorsally inflated and unornamented, posteriorly tapering to slight 

 median notch, seen in dorsal view. Uropodal rami distally shallowly serrate, 

 exopod 2.5 times longer than wide. 



RECORDS Puerto Rico, intertidal to 0.5 m; in algae on rocks, and under 

 Chiton tuberculatus and C. marmoratus. 



