152 bulletin: museum of comparative zoology. 



to the outer circular muscular layer (PI. 13, fig. 81), but back 

 toward the ne])hridial region it breaks through the outer circular, 

 diagonal, and longitudinal muscles, and takes up a position just out- 

 side tlie enormously thickened inner circular muscles. Back in the 

 intestinal region it Ues directly upon the proboscis sheath (PI. 14, 

 fig. 83) . 



A ventral median nerve is also present. This nerve likewise lies 

 outside the outer circular muscles in the anterior eso])hageal region 

 (PL 13, fig. 81), and passes inward to occupy a position between the 

 two circular muscular layers farther back. It is most conspicuous 

 where the inner circular muscles are thickest (PI. 13, fig. 82) , as 

 figured by Burger for C. jxitagonica. 



The lateral nerves lie close to the diagonal muscles in the anterior 

 esophageal region, but toward the nephridial region pass somewhat 

 internally and lie imbedded in the midst of the longitudinal muscles 

 (PI. 13, 'fig. 82 ; PL 14, figs. 83, 87). 



Cephalic sensory pits. — A number of small sensory pits are 

 sitiiated on the dorsal surface of the head in the median line between 

 the brain and the tip of the snout. Such organs were first dis- 

 covered in Carinoma tremaphoros by Miss C. B. Thompson (: 00, 

 p. 627), and have since been found by Bergendal (:03, p. 610) in 

 (J. armandi. 



Whether future study will reveal their presence in G. patagonica 

 Biirger is of course a matter of speculation, but since they are known 

 to occur in three of the four described species of the genus and have 

 been found in no other nemerteans they may be looked upon as 

 probably characteristic of the genus. 



In the first specimens of C mutabilis which I examined, these 

 sense organs were very inconspicuous, and were not mentioned in my 

 previous description of the species (:01, p. 20). They are actually 

 present, however, in all of my prej^arations. 



Their structure agrees closely T\ath the account given by Bergendal 

 (:03, p. 610), but in no case are they sufliciently Avell ])resei'ved to 

 reveal any other details of structure than those mentioned by IVIiss 

 Thompson and by Bergendal (see p. 62). They agree with Ber- 

 gendal's description and differ fi'om those described by Miss Thomp- 

 son in being well separated from the surface of the integument and 

 in being connected with the exterior by a narrow canal only. Ber- 

 gendal states in a later paper (: 04) that such apparent differences 



