ANATOMICAL NOMENCLATURE. 



125 



In measuring tlie eyes, the unit for determining the distance between 

 any two, as MF or MR, is the diameter of the pair under considera- 

 tion. In measuring the distance between the middle group of eyes, 

 whether of the front or rear row, and the side group, the unit of measure 

 is usually the linear space occupied by the same, that is, the distance from 

 outer margin to outer margin ; in other words, the width of the front or 

 rear sides of the middle quadrilateral. This line is spoken of technically 

 as the " area " or the " alignment." (Fig. 87, ar.) Thus the area of MF 

 is the line from the outside of one midfront eye to the outside of the other. 

 Sometimes the space between the midfront eyes is also used as a unit. 



The clypeus (cly, Fig. 87) is that part of the face lying between the 



front row of eyes and the anterior lower margin thereof, where it meets 



tlie mandibles. The clypeus is spoken of as "high " or " low," as 



2 J^P®"^ the space above named is greater or less ; or sometimes the words 



" wide " and " narrow " are used as equivalent to the above. The 



Bpigy 

 num 



height or width of the 

 clypeus is measured by the dis- 

 tance of its margin from the two 

 midfront eyes, and the diameter of 

 one of these is the . unit for such 

 measurement. 



The views of the epigynum or 

 external part of the female genital, 

 in the various plates, are taken with 

 the spider lying upon the back and 

 the observer looking down upon her 



from the direction of the spinner- *'i°- S^- Crscorselet; eg corselet grooves; 



*■ fosse ; ba, base of corselet ; md, indentatK 



ets. The drawings therefore show 

 the lower side of the organ unless 

 otherwise specified. 



The following terms are used in 

 describing the ceiihalothorax : The dorsal part is known as the " corselet " 

 (Fig. 91, crs), of which the posterior part is the base (ba), and this is 

 usually smooth, truncated, and indented where overhung by the 

 abdomen. The depression on the summit is the median fosse, or 

 simply " fosse " (fs) ; the slight furrows extending from the fosse 

 to the insertion of the legs are " corselet grooves " (eg) or furrows. The 

 line of union between caput and corselet is the " cephalic suture " (c.su) ; 

 that part of the head extending from the suture to the vertex I have called 

 the caput (cap), as distinguished from the vertex or forehead and the face. 

 The under part of the cephalothorax is the sternum (Fig. 92, str), which is 

 a more or less oval or cprdate or subtriangular shield, sometimes much 

 indented or scalloped at the coxal insertions and pointed at the base (ba). 

 Opposite the coxse, in some species, are slight eminences technically referred 



str 



Fig. 92, 

 Cephalothorax and Parts thereof. 



fs, median 



fosse; ba, base of corselet ; ind, indentation thereof; 

 cap, caput : mg, margin of corselet ; c.su, cephalic 

 suture ; es, eye space ; o.q, ocular quad. Fig. 92. Ster- 

 num and mouth parts. Str, sternum ; s.co, sternal 

 cones ; ba, base of sternum ; ap, apex of same ; lab, 

 labium ; mx, maxillae. 



Cephalo 

 thorax. 



