124 BRITISH TYKOGLYPHIPTE. 



Nalepa found that in Garpoglyplius some few pass on 

 and are inserted into the proximal edge of the femur. 

 Four pairs of large muscle-bundles arise from the 

 lateral dorsal cuticle, and pass diagonally downward 

 between the body-wall and the alimentary canal ; they 

 are inserted into the proximal edge of the coxa. 

 These are the levator (or retractor) muscles of the 

 coxa3 ; they are attached by strong tendons ; a portion 

 of a pair of these muscles, cut short by the section, is 

 shown in fig. 3, mlc. 



The depressor muscles of the coxae (fig. 3, mdc) are 

 very differently arranged and require a little more 

 explanation. In the higher Acarina, such as the 

 Gamasidae, Bdellidae, etc., the organ which is known 

 in many other Arachnida, and even in some other 

 Arthropoda, and which is called the endosternite (or 

 episternite), is highly developed. In the above-named 

 families of Acarina it consists of a largish, tendinous, 

 horizontal plate lying below the ventriculus and above 

 the brain ; it is suspended from the dorsal integument 

 by bands of muscle and of connective tissue. In Bdella 

 it is a thick plate, which in B. vulgaris seems to show 

 signs of being formed by the compression of a sack ; at 

 all events it has stout upper and under walls which, in 

 transverse sections of the creature, show a narrow but 

 distinct lumen between them. It forms practically an 

 internal skeletal piece for the attachment of numerous 

 muscles, principally the great muscles of the legs. In 

 such Tyroglyphidae as have been investigated this 

 organ exists, but it is reduced to its smallest possible 

 dimensions ; so small that it seems to be little if any- 

 thing more than a point where the tendons at the 

 inner ends of the depressor muscles of the coxae are 

 joined to one another. Nalepa considers that this is 

 what the organ in Oarpoglyphus really is ; he calls it a 

 " Knotenpwilde" and says it lies below the ventriculus 

 and above the posterior end of the sub-oesophageal 

 ganglion. In G-lycypliagus platycj aster it is not a point, 

 but more a small longitudinal blade, the anterior end 



