Pacific Coast of North America, 329 



Family XIII. OniscidaB. 



Analytical Key to the Genera o/ Oiiiscida3. 



f. Flagelkim of external anteuase biarticulate. 

 External opercular ramus of the first, second, 

 and rarely of the third or all the pairs of tlie 

 abdominal appendages furnished with trachea. 

 h. Lateral lobes of the head large ; frontal lobe 

 more or less projecting. Eyes subdorsal. 

 First two abdominal segments generally very 

 short ; three following ones large, witla large 

 epimera. Terminal segment not reaching 

 beyond the epimera of preceding segment. 

 Uropoda somewhat even, longer in male than 



in female 29. ForcelUo. 



b'. Lateral lobes of head small, hardly projecting ; 

 frontal lobe obsolete. Eyes lateral. First 

 two abdominal segments scarcely shorter 

 than those following. Epimera of all the 

 segments small. Terminal segment ex- 

 tending beyond the epimera of preceding 

 segment. Uropoda subequal in both sexes . . 30. 3Ie(i)po/iort/ius. 

 a'. Flagellum of external antennce triarticulate. 

 External opercular ramus of abdominal append- 

 ages containing no special respiratory organ. 

 b. Front of head produced at the middle and at 

 the sides in tubereles ; lateral tubercles horn- 

 like. Epimera of abdominal segments mode- 

 rate or small 31. Alloniscus, 



b'. Front of head not produced, with lateral lobes. 



Epimera of abdominal segments large .... 32. Lyiwobius. 



29. POECELLIO, Latreille. 



Analytical Key to the Species of Porcellio. 



a. Surface of body smooth. 



b. Frontal median lobe of head rounded, a 

 little produced. Articles of the flagel- 

 lum of external antennfe equal in length. 

 Last segment of the abdomen with its 



extremity widely rounded 72. P.formosus, Stuxberg. 



b'. Frontal median lobe of head more 

 acute, minute. First article of the 

 flagellum of external antennae equal 

 in length to the other or a little 

 longer. Last segment of the abdomen 



with its extremity acute 73. P. lavis, Latreille. 



a'. Surface of body closely and roughly 



granulated 74. P. scaber, Latreille. 



72. Porcellio for mosus J Stuxberg. 



losus, Stuxberg, CEfversigt af Vetensk.-^ 

 p. 57 ; Budde-Lund, Crust. Isop. Terresti 



Hah. San Francisco and San Pedro, California. 



Porcellio formosus, Stuxberg, ffifversigt af Vetensk.-Akad. Fiirhandl. 

 1875, no. 2, p. 57 ; Budde-Lund, Crust. Isop. Terrestria, 1883, p. 141. 



