NEOMENIA VERRILLI. 209 



Between the bases of these folds and the somatic musculature are large 

 numbers of gland cells separated into small lobules by connective-tissue septa 

 between which blood sinuses make their way. No traces of ductules are appar- 

 ent though there are evidences here and there, possibly a post mortem effect, 

 that some of the cells have released their hold and are free in the blood stream, 

 while others, attached by very slender stalks, appear to be in process of libera- 

 tion. In a general way these elements remind one of the concrement cells as 

 described by Brock (1883), but there is no definite evidence that they are 

 homologous or that they function similarly. 



The circulatory system has suffered to a greater extent from the mutilation 

 of the specimen than any other set of organs, but so far as determined it con- 

 forms closely to the neomenian type. The pericardial cavity is of moderate 

 size only, and the ventral displacement indicated in the reconstruction (Plate 3, 

 fig. 1), may be an abnormal state of affairs. As indicated there is a shallow 

 pouch-like expansion of the forward wall in the neighborhood of the reno- 

 pericardial openings, but with the exception of a somewhat thicker, slightly 

 corrugated wall there are no indications that it may play any especial function. 



The heart is a two-chambered organ, the blood from the branchiae and the 

 dorsal part of the posterior end of the body entering the hindmost section. 

 There are indications of a valve guarding the union of the two divisions. The 

 clearly defined dorsal aorta, holding the usual position and supplying the cus- 

 tomary organs, makes its way to the head cavity, and there conmiunicates with 

 an extensive system of spaces which in turn soon combine to form the median 

 ventral sinus and that of the general visceral cavity. In the posterior end of 

 the body, about the level of the anterior end of the shell gland, the first named 

 of these canals rapidly diminishes in size, while the other communicates with 

 spaces leading into the branchiae and beyond them into the heart. 



The nervous system is more than usually well-defined, and for this reason 

 more than ordinary care has been taken to determine the position of the vari- 

 ous ganglia and their more important branches. The brain occupies the usual 

 position above the atrial cavity, and with the exception of its comparatively 

 small size presents no especially noteworthy features. As usual it originates 

 on its anterior face several nerves that are distributed to the atrium and the 

 adjacent body wall; and laterally it gives rise to the connectives passing to the 

 labiobuccal, lateral, and ventral ganglia. The last named connectives like the 

 brain, are of exceptionally small calibre, and lying loosely in the visceral cavity 

 may be traced to the region of the outlet of the anterior pedal gland where 

 they unite with the ventral ganglia. Close to the point of union the ganglia 



