160 PROCEEDINGS OF THE ACADEMY OF 



I ma}' here mention that Tiyon (Am. Jour. Conch., II. 246) 

 erroneously includes in Macrocyclis a true species of Zonites, Z. 

 Ulliotti, characterized by caudal mucous pore, parallel longitudinal 

 furrows above the margin of the foot, and the presence of perfect 

 lateral teeth. 



The side teeth of Macrocijclis at first sight, especially when 

 seen from below, appear to be of the purely aculeate type, as the 

 marginals in Zonifes and Umax. From this, one is inclined to 

 consider them all as marginals, and to declare that no true lateral 

 teeth exist, thus making Macrocyclis to agree with Glandina in 

 this particular also. A more careful study shows us that the 

 teeth nearest the median line are modified from the aculeate type, 

 though they do not have the distinct form of the laterals of Zo- 

 7iites, with decided cusps and cutting points. They seem rather 

 to represent those teeth of Zonites which show the transition from 

 the laterals to the marginals (see pi. II., fig. 2, the second lateral 

 tooth of Z. Isemgatus). It may be said, therefore, that the lateral 

 teeth are entirely wanting in Macrocyclis^ the first side teeth 

 being laterals in the transition state, the balance being pure mar- 

 ginals. (See, however, M. euspira, below, which has a lingual 

 membrane of Glandina.) The base of attachment of these tran- 

 sition teeth is like those of the marginals, i. e., sole-like, except 

 that the lower lateral expansions are more developed and angular, 

 and in concava and Voyana the lower edge is excurved rather 

 than incurved. The cusps are long and slender, lengthened into 

 cutting points ; the teeth are unsymmetrical by the greater de- 

 velopment of the outer subobsolete side cusps, both of these cusps 

 being distinctly indicated b3' expansion. In M. Vancouverensis 

 there is apparently a small sharp side point on the inner side of 

 the cusp. I am not certain of its character, and have not ven- 

 tured to figure it, excepting on the second tooth in fig. 4a. This 

 process is seen on the first six teeth only. The balance of the 

 teeth beyond the transition teeth in all the species are marginals 

 of the pure aculeate type. They vary in sharpness in different 

 parts of the same membrane, as will be seen by comparing my 

 figure ib of 31. Vancouverensis with the marginals in profile given 

 by Morse (see above fig. 2). In 31. D^iranti the extreme mar- 

 ginals are large in comparison with those of the other species. 



In studying my figures, it must be remembered that fig. 3a, 5a, 

 and 4c are drawn as seen from above, to show the form of the 



