ICHTHYOMENIA POROSA. If)!) 



cavity, or cirrose portion of tho digestive tract, but witli reference to the i)luir}iix 

 it is normally situated. As usual branches pass out from the anterior surface 

 of the brain to unite with ganglionic masses about the bases of the cirri which 

 they appear to iimervate and three pairs of connectives unite with the labio- 

 buccal, pedal, and lateral nervous systems. Connectives and commissures, 

 agreeing closely in number with the gut pouches, join the pedal and lateral cords 

 throughout the body. In the region of the cloaca the pedal cords diminish in 

 size and finally disappear, and the lateral cords likewise diminish considerably 

 in calibre, and are united by a commissure which unlike the usual type, is devoid 

 of ganglion cells. 



The labio-buccal comiectives, imbedded in the pharyngeal wall, attach to 

 large ganglia lateral to tlie salivaiy ducts. Owing to the munbers of salivary 

 ductules it is very difficult to trace nerves in this region and determine if there 

 be more than the one commissiu'c imiting these ganglia beneath the pharynx. 



Ichthyomenia porosa, s]i. iiov. 



Upwards of twenty individuals of this species were taken in one dredge 

 haul (Sta. 4400) off the coast of southern California, and two additional specimens 

 were captured in the same locality at Station 4402. In both cases the bottom 

 consisted of green mud at a depth of 500-507 and 542 fathoms respectively. 

 All were unattached and there is no evidence whatever regarding their mode 

 of life though it is possible that they may be parasitic upon some of the sea pens 

 (Pennatul'idae), of which three species abound in this locality. 



There are slight inequalities in size due to differences in age and sexual 

 maturity but the average length is approximately 10 mm. with a diameter of 

 1.2 mm. The head region is indistinct (Plate 3, fig. 4) and externally is chai'ac- 

 terized merely by a very slightly greater diameter than that of the body. Poste- 

 riorly, in an uncontracted state, the body terminates in a pointed extremity, 

 but in other cases it may become blunt and where the cloaca is opened widely, 

 trumpet-shaped. A pedal groove is present and as usual extends from the hinder 

 border of the mouth to the cloaca! opening with which it is continuous. The 

 opening of the anterior jiedal gland is usually very distinct, having the appear- 

 ance shown in Plate 5, fig. 6. 



Of the spines covering the body by far the most abundant are exceedingly 

 delicate, of a pointed ovate shape (Plate 37, fig. 1), 0.024 mm. long, and are 

 imbricated, forming a single layer. In the neighborhood of the ventral furrow 

 these are associated with a somewhat similar type, 0.0594 mm. long, with 



