140 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



Table 2. — List of spinasternal muscles considered 



Also included are icv-cxiX, corresponding to isps-cxi, ^sps-cxs; and Isps- 

 3ils, corresponding to 2sps-iils, 3sps-2ils. See text. 



Notes to Table 2. 



1. The muscles 2sps-iils, 3sps-2i}s, and Isps-3ils are regarded as having pro- 

 vided parts of the definitive 2sps-pli, 3sps-ph, Isps-pU, respectively, in Lepisma; 

 so that the form of muscles listed in the table is believed to be represented in 

 thysanurans. 



2. The muscle 2sps-3ils is believed to furnish part of the definitive 2Sps-Iils 

 in certain Pterygota. See text. 



3. Ligamentous portions of the endosternum of Lepisma, as described by 

 Barlet (1951), are taken to correspond to pterygote muscles or ligaments, as 

 follows : 



Barlet, 195 1 This paper 



m-b-q isps-fui, etc. 



n isps-iils, etc. 



»' isps-epSi 



Glossary of abbreviations 



cz' cervical sclerite 



ex coxa 



eps episternum 



fn furca, furcal arm, segmental sternal apophysis 



ils intersegmental laterosternite 



m-b-q, n, n' . .■parts of endosternum of Lepisma (Barlet, 1951) 



pi pleuron 



.y segmental sternum 



sps spinasternite or spina 



X cruciate, used of a muscle whose origin and insertion are on opposite 



sides of the midline 



The abbreviations are used throughout the text to form designations of the 

 various muscles discussed, by placing a hyphen between abbreviations for the 

 structures between which the muscle is stretched. Subscripts, arabic for the 

 thorax and roman for the abdomen, indicate the segmental affinity. Interseg- 

 mental structures are preceded by the appropriate numeral, beginning with for 

 the cervical intersegment and / for the first abdominal intersegment. The cus- 

 tomary designations, icv, 2cv . . . etc., for the cervical sclerites are retained. 



