l.nl'IKiBKANCIlS. 



665 



Fi.i:-. 1711. Anatomy uf Synrjiuithns li/jihle. Afk-r A. Retzius. 



A: Male, witli llic iiljiloininnl wall opened and folded outwards and tlie 

 niarsiipiiini, in wlnVli appear tlie cavities left by tlje eggs, distended. 



/(, liver; vit, air-bladder, with tbe anterior, thin-wallcd part pointed 

 and obliquely divided from the posterior; t, testes; pa, anal fin: vu. 

 urinary bladder; /, intestine, opened for a short distance at tbe vent; 

 ug, nrogenital aperture, behind (below) the vent, which is opened. 



JS; Female, with the abdominal wall opened and folded outwards. 



A, liver; cf, gall-bladder; yx/, anal fin; ip intestine, at the month of 

 the galldnct coming from the right side (in the figure the left); !.>, 

 posterior part of the intestine, opened in order to show tbe valve that 

 divides the intestine from the rectum, which is also opened as well 

 as the vent; ov, ovaries; vti, urinary bladder; tig, urogenital aperture. 



Opening just lichind (lie \cnt. TIio urinary bladder is 

 loiifi; and nai'iMw, Tu's on tlic left side, and coasts the 

 left sc.\ii;il oriiiiii. 'I'lic ;iir-liI;Hl(l<T is large and coasts 

 tlie iiiijicr \\;dl of tiie alxlomiiial cavity foi' at least 

 ()nc-li;df or Iwo-tliirds of tlie lengtli of the latter. 



The I'ilis arc \\;intiiig. Among the otiier pecidiari- 

 ties of the skeleton the structure of the shoulder-girdle 

 is es|)eci;dl\' rcinark;il)lc. The postteinporal bone (fig. 

 171, /)/) (•(i;ilcsccs with the mastoid bone (epoficum) of 

 the skull and is con ercd in a (Janoid fashion by a plate- 

 like hi\cr, pointed iiehind. 'i'he sui)raclavieular bones are 

 \\;uitiiig: hut the id;i\ i(de (il) is all the larger. Tliis 

 hone is T-sh;iped, with the upper (iKirizoutal) linr united 

 to the transxerse processes of the first two \ertebr;e. 

 The first transverse process is directed backwards, and 

 so long that ;dl the .•luterioi- upper branch of the cla- 

 vicle iua\ be contiguous with it: while the second of 

 these processes, which is comparatively sliort, and onh' 

 slightly expanded at the top, adjoins the angle between 

 the horizontal and \ ertical branches of the clavicle. The 

 ofitside of the cdavicle is co\ered by the three plates on 

 each side of the bod^■ which form the first (foremost) 

 ring; and in Si/iif/i/dt/ins kciis the inner jjrong of the 

 vertical shaft, which is forked at the bottom, in the T- 

 form of the clavicle, is supjiorted on the first abdominal 

 plate belonging to tlic same ring. This ])late is wanting 

 in Sijtujiiufhiis ti/j)lili\ where the support is therefore 

 given by the lower kitcral phite. Onty the anterior 

 margin, howe\er, of the middle lateral plate in this ring 

 is united to the middle of the shaft in the T-form of 

 the clavicle, the rest of this plate lying as a covering over 

 the muscular mass of the pectoral tin, in the middle of 

 which mass we find the extremely thin scapulo-coracoid 

 disk (sr) together witli the four basal bones (fig. 171, 

 has) of the ])ectoral tin. This disk is not divided here 

 into its ordinary component jiai-ts (the shoidder-blatk' 

 and the coracoid bone), and is extended between the 

 hind part of the upper (horizontal) branch of the clavicle 

 and the inner pi-ong of the \ertical shaft of the clavicle, 

 without touching this bone at any other point. At this 

 lower end of the cla\ icie, howe\cr. witltin the lowei- end 

 of the scapulo-coracoid disk and above the inner side of 

 the first two abdominal phites in Si/nffnatliKs acus, lies 

 one interclavicle (id), which meets both the clavicle and 

 the s;iid disk (fig. 171,.sr). }\i'ither in Synr/iiafli lis (icKS 

 nor in S. ti/phlc ha\e we succeeded in finding more 

 than one such interclavicle, though according to I'ak- 

 Ki;i! the formei' species possesses two. 



