136 McMURRICH. [Vol. IV. 



the discrepancy between the number found in the Beaufort 

 specimens and that given by Verrill is probably in accord with 

 the smaller size of my specimens. A tentacle of the oral series 

 corresponds to and is opposite each marginal tentacle, and both 

 series seem to be arranged in three cycles, not four, as I stated in 

 my previous paper, but I was not able to ascertain the relations 

 of the various cycles in the two series. The accounts given by 

 von Heider ('79) and Fischer ('89) of these relations in C. mem- 

 branaceiis differ materially. The number of cycles, however, 

 does not have the same significance here that it has in the 

 Hexactinise, and the arrangement of the tentacles in cycles is 

 no doubt, as von Heider suggests, altogether mechanical, and 

 due to crowding, and accordingly their relation in the marginal 

 and oral series, and the number of the cycles in which they are 

 arranged, may vary. 



2. Internal Structure. 



On laying open a specimen of C. Americanns by a longi- 

 tudinal incision, the appearance presented is that indicated in 

 Figure i, PI. VII., in which, however, the disc and tentacles have 

 been omitted. In the upper part one sees the stomatodaeum 

 with a well-marked longitudinal groove — the siphonoglyphe. 

 By close examination it may be seen to be finely grooved lon- 

 gitudinally, each groove corresponding to a mesentery ; a few 

 transverse grooves may usually be seen, but they are more or 

 less irregular, and are no doubt due to contraction. Its lower 

 margin is usually reflected, so that a transverse section in this 

 region gives the appearance represented in Figure 3. 



The mesenteries are arranged on a very different plan for 

 what has been described for C. metnbraiiaceus and C. borealis, 

 Danl. On first laying open a specimen of C. Americanus, one 

 sees that more than one pair of mesenteries reach the posterior 

 extremity of the body, and yet all do not extend so far. In the 

 specimen figured twenty-three well-developed mesenteries are 

 present. The total number of mesenteries is really ninety- 

 two, as will be seen later, but of these only twenty-three 

 pass more than half-way down the column, and it is to the 

 arrangement of these that I wish first to direct the atten- 

 tion. Extending the entire length of the body from the 

 region of the siphonoglyphe is a pair of mesenteries corre- 



