656 DESCRIPTION OF PLATE, 22. 



when the animal was young, but has since been closed 

 externally by sand or shelly matter, and internally by the 

 upward prolongation of the horny disc ; b, rims of an 

 inorganic, calcareous deposit, by which the narrow end of 

 the orifice is kept of the due degree of narrowness. 

 Fig. 5, Longitudinal section through the outer envelopes of a very 

 symmetrical specimen, giving a lateral view of the included 

 body. 



a, point at the lower end of the orifice of the capitulum, 



leading into the sack. 



b, end of adductor muscle. 



c, mass of branching ovarian caeca, much developed and 



protuberant on the under side. 



d, basal point of the quasi-peduncle, projecting beyond the 



level of the horny disc (n, h). 



e, sack or open cavity : of the two branchiae or ovigerous 



fraena, one has been removed with the outer envelopes, 

 the other is hidden by the projection caused by the 

 medial distended mass of the ovarian caeca. 

 e', lateral line of junction of the body to the outer envelopes ; 

 which latter have been here cut through in removing the 

 near half of the capitulum and peduncle. 

 f> notch separating the capitulum or upper part from the 

 peduncle or lower part of the external covering : this 

 notch varies much in depth. 

 <7, the end (homologically the carinal end), of the orifice 

 leading into the sack, where the cutting of the outer 

 envelopes has commenced. 

 h h, horny disc, cut longitudinally down the middle. 

 h, first pair of cirri. 



?', prosoma (homologically the second thoracic segment). 

 k, the thoracic segment, which would have borne the second 



pair of cirri, had such existed. 

 /, thoracic segment, which should have borne the third pair. 

 m, thoracic segment, which should have borne the fourth pair. 

 n, thoracic segment, very small, bearing the fifth pair of 



cirri. 

 n'y fifth pair of cirri, only one cirrus on the near side being 



represented, 

 o', sixth cirrus, borne on the last thoracic segment, too small 



to be shown. 

 p, caudal appendages. 

 6, one side or lip of the orifice leading into the sack, greatly 

 enlarged, seen on the inner side, formed of an inner mem- 

 brane, b, (on which the long hairs and an S-like band of 

 spines, too fine to be plainly represented, are placed), and an 

 outer membrane c, studded with short, thick spines, the 

 corium between these two membranes having been re- 

 moved; a, projection at lower end of orifice; g, upper 

 end of orifice, showing the point where the corresponding 

 side or lip of the orifice has been cut away. 



