ANATOMICAL NOMENCLATURE. 



125 



In measuring the eyes, the nnit for determining the distance hetween 

 any two, as MF or MR, is tlie 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 



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



Clypeus j_jjg space above named is greater or less ; or sometimes the words 



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

 num. . ^ 



height or width of the es 



clypeus is measured by the dis- 



str 



ap: 



Fu:. 92. 



Cephalothorax and Parts thereof. 



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- ]•"■;;• "■ Crscorselet; eg corselet grooves; fs median 



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



etS. The drawings therefore show cap, caput ; mg, margrin of eorselet ; c.su, cephalic 



.11 • J j; J.1 i„ suture : es, eve space ; o.q, ocular quad. Fu;. 92. Ster- 



the lower side of the organ unless ^^^^ a„d mouth parts. Str, sternum; SCO. sternal 



otherwise specified. cones; ba, base of sternum; ap, apex of same; lab, 



,ni c 11 • i. 1 ■ labium; mx, maxillse. 



The rollowmg terms are used ni 

 describing the cephalothorax : 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 

 Cephalo- g^i^^Qj^g^^ rpj^g 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 cordate or svd:)triangular shield, sometimes much 

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

 Opposite the coxa3, in some species, are slight eminences technically referred 



