104 E. A. Andrexo8 — Anatoni)/ of the t^pider Crab. 



l)Ie, whicli glides over tlie edge of the left in chewing, presents a 

 slight tubercle at the apex of its curved cutting edge (c, fig. 8)- 

 Each mandible (fig. S), projecting downward from the sternal wall, is 

 articulated along its outer edge to the edge of the endostoina {en, 

 fig. 20, this is the calcified sternal plate which forms the roof of the 

 anterior part of the peristome and sends back a branch on either side 

 of the moutli), while the inner edge {a, fig. 8) articulates pos- 

 teriorly to a process from the sternum of the following segment. 



Near this latter articulation a very long tendon {t') arises from the 

 edge of the mandible, and, passing obliquely upward by the side of 

 the stomach, is connected with an adductor muscle (///, fig. l), origi- 

 nating from the carapace. The mandible is continued within the body 

 cavity as a stout process, hollow on the posterior face, and is divisible 

 into a vertical («, fig. 8) and a horizontal or posterior branch {in). 

 The former, extending up by the side of the stomach, is articulated 

 externally to a large tendon {t), to which is attached the large trian- 

 gular mass of abductor muscles extending outward and fastened to 

 the carapace («<, fig. 1). From the inner face of this vertical process a 

 large slender abductor muscle j)asses downward and inward in front 

 of the long tendon oi'the smaller mandibular adductor, and is attaclied 

 to the apodemal process arising between the first and second maxillae. 

 The j)OSterior part of the process {ui, fig. 8) is articulated with the 

 anterior side of the framework to which the second maxilla is 

 attached ; and bears on its horizontal edge a slender tendon [t") 

 which arises vertically and is joined to the carapace by a small 

 abductor muscle [a, b, fig. J), which is accompanied by a long muscle 

 running down to the first maxilla. The mandibles thus move trans- 

 versely, with a slight I'oUing motion. 



Inserted close behind and partly overlying the mandibles are the 

 first pair of maxillje (fig. 9), small delicate organs, divided into three 

 lamelliform lobes or branches, the central and inner ones of which 

 (c, b) bear stout bristle-like seta\ The external portion {en, fig. 9) 

 bears only filiform setaj. 



The second pair of maxilhe (fig. 10) are more important as acces- 

 sory respiratory organs than as organs of mastication. They arise 

 behind the first, but noticeably farther fi-om the median line. The 

 two lobes nearer the median line {b, c, en) are small and delicate, 

 the outer {b) is cleft. The external lobe (en) bears long delicate seta'. 

 Far the largest part of the appendage is the scaphognathite {s(/), 

 the large outer lobe which forms a curved lamina, prolonged longi- 

 tudinally, and lying horizontally in the efterent canal. It acts con- 



