Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
AND ENDOSKELETAL SYSTEMS OF LIMULUS. 337 
. Shows the relation of the pericardium (Pc) and the venous collecting sinus (vc) 
to the other parts and to one another. To be especially noticed are the 
pericardio-ventral or veno-pericardiac muscles (68): the vertical mesosomatic 
muscles (12): the ventral pygal muscles (9, 10, 11): the muscular stomach 
(s) with its muscle (66) to the subfrontal area (sfa). Also the intertergal 
muscle (78) flexing the abdominal upon the thoracic region. 
. Shows the plastro-tergal muscles (49 to 54): the genital duct in appendage vil: 
the inter-entapophysial muscles (4): the course of the ventral longitudinal (5) 
and intersternal muscles (5), with their various slips to the entapophyses. 
Also the vertical abdominals (12). 
. External view of two entapophyses of the left side (twice nat. size) showing the 
cartilaginous interentapophysial ligament (ec) swelling out to partly embrace 
the entapophysis, and serving for the attachment of various muscles which 
pass to the mesosomatic appendages. ‘The area of attachment of two of the 
external branchial muscles (20) is shown. 
. Internal view (mediad face) of two entapophyses of the right side (twice nat. 
size). The cartilaginous interentapophysial ligament is seen, and various 
muscles attached to the entapophysis itself. Also the area of attachment 
of two of the vertical mesosomatic muscles (12) is seen on the tergite. 
. A three-quarter view from in front and within of an entapophysis and cartilage. 
. A three-quarter view from behind and without, showing the cut end (éct) of 
that part of the inter-entapophysial ligament that passes from one swelling to 
another. The swelling of the ligament is deeply cupped and fixed to the 
chitinous entapophysis. It contains a core of capsuligenous tissue, whilst 
the rest of the ligament consists of fibro-massive tissue. 
PLATE LXXVI. 
. Inner face of the prosomatic and mesosomatic carapaces, showing the areas of 
attachment of the various tergal muscles. [Unfortunately this figure is very 
inaccurate and incomplete in respect of the areas of muscular attachment, 
and must not be relied upon in that matter—E. R. L.] On the right half 
the areas are left uncoloured, and are more plainly limited than on the left 
half. The entapophyses are shown, and the ridge (77) on each side, corre- 
sponding to a depression on the exterior. The lateral parts of the terga have 
a chitinous network raised upon their inner surface. In the mesosomatic 
portion is shown a part (x) of the sternal region which rises to meet the 
tergite. 
Fig. 2. Shows the relative positions of the entocoxite (whose knobs (£), to which the 
tergo-coxals are attached, are seen), the prosomatic entochondrite (plastron) 
(P), and the mesosomatic entochondrites (s). The hollow tendons (¢s) of the 
3E2 
