Parker AnD Rica—Ox the Myology of Patinurus Edwardsir, Hutton. 163 
outer limb of the envelopig muscle, and constitutes what we propose to call the 
external flexor of the segment into which it is inserted : it is connected by a narrow 
ligamentous band with the longitudinal flexor of the segment next im front, and from 
it the oblique flexor arises. By pressing the longitudinal flexors aside the transverse 
muscles are seen as well from below as from above. 
Anteriorly the ventral muscles are continued into the thorax by numerous bands 
arising partly from the inner surfaces of the epimeral plates, partly from the maxillary 
apodeme or foremost bar of the endophragmal system. They act, for the most part, 
as flexors of the first abdominal segment, and may be called the ¢hovacico-abdominal 
muscles, the separate slips bemg most conveniently distinguished by numbers. 
A large two-headed slip (1) arises from the maxillary apodeme; a second (2), also 
double-headed, arises by an immer head (2’) from the maxillary apodeme, by an outer 
head (2") from the epimeron of the third thoracic segment ; a third (3) arises from 
the third thoracic epimeron, a fourth (4) from the maxillary apodeme, a fifth (5) from 
the third thoracic epimeron, and a sixth (6) from the fourth epimeron, z.e., that 
corresponding to the first leg. All these unite to form a sheet of muscle partially 
divisible into longitudinal strands which are inserted into the first abdominal sternum. 
They therefore constitute the longitudinal flexor of the first segment. The innermost 
ventral strands, formed mainly from Nos. 1, 4 and 5, exhibit faint transverse tendinous 
intersections, and No. 2 unites with its fellow of the opposite side just ventrad of the 
thoracic transverse muscle. 
Finally a seventh slip (7) arises by two heads (7’ and 7’) from the epimeron of 
the fifth thoracic segment and divides into three bundles. One of these (7*) joins 
the slips mentioned in the preceding paragraph, becoming the outermost strand 
of the longitudinal flexor of the first abdominal segment; the second (7°) passes below 
the thoracic transverse muscle, and, as will be seen hereafter, joms the transverse 
muscle of the first abdominal segment; the third (7°), placed dorsally, passes distinctly 
backwards and is encircled by the thoracic enveloping muscle. As will be seen this 
latter bundle is the commencement of the central muscle of the abdomen, presently 
to be described. 
The greater part of the foregoing descriptions can be verified without the 
severance of a single muscle; to make out the connection of the various bands with 
one another it is necessary to cut and reflect the superficial ones. 
When the enveloping muscles of the thorax and of the first five abdominal 
segments are cut through by a longitudinal incision and reflected, each is seen to 
wrap round a curved cylindrical band, the cextval muscle of Milne-Edwards. This 
turns dorsad at its anterior end and, emerging between its own enveloping muscle 
