NO. 2134. NOTES ON CHRYSODOMUS—DALL. 209 



ence in the larva of a cartilaginous primal cell, lost in the ovicapsule 

 before emergence, and of which the shelly pointed apex is the 

 secondary stage. 



The first fundamental type may for brevity be termed the Chrys- 

 odomoid. The second, after its characteristic genus, the Siphonor- 

 bitoid. The latter may be described as follows: It has a turbinoid 

 aspect when viewed from above and is always depressed or at least 

 blunt; it is regularly coiled; it begins with a smooth minute apical 

 cell which develops a whorl or sometimes a whorl and a half, then 

 assumes a sculptured surface, composed of one or more sharp spirals 

 crossed by rather distant thin sharp axial riblets for two or three 

 regularly enlarging, moderately inflated whorls, usually ending ab- 

 ruptly but sometimes merging gradually into the adult sculpture; 

 and is more or less invested with a distinct, sometimes villous, 

 periostracum. This type of nucleus is common not only to the group, 

 SipJionorhis, but also to Mohnia^ Kryptos^ and the aberrant Tro- 

 schelia^ which, by its dentition, is allied to Fasciolaria and Fusinus^ 

 perhaps indicating a closer relationship between these genera at an 

 earlier period. 



The Siphonorbis nucleus is figured by Friele on plate 2, figs. 19, 

 22, 30, and 34 ; and one with the original sculpture eroded, at fig. 25. 



As far as sculpture is concerned the group of Colus divides itself 

 naturally into those with spiral sculpture, but without axial riblets 

 {Colus sensu sti^cto), in which the spiral sculpture may be strong 

 or feeble, though in some of the latter it is almost obsolete, the shell 

 without careful and even microscopic scrutiny appearing smooth; 

 and those with axial plications, which are frequently confined to 

 the early whorls and absent or obsolete on the later ones. There is 

 also a small group {Kryptos) in which the axial sculpture may be 

 developed only as nodules at the shoulder. The latter has not been 

 examined anatomically and has been claimed as a member of another 

 family. 



In general form we have infinite gradations from the elongated 

 type, simulating Fusinus, with narrow, nearly straight, and produced 

 canal, to those species in which the canal is short and recurved, or 

 wide and hardly differentiated from the aperture ; or Buccinoid and 

 scarcely to be differentiated ivom. Buccinum except by the operculum. 

 There is also a small group in which the shell is plicate and usually 

 dark colored and, compared with the typical forms, quite minute 

 in size. 



The group of Ghrysodomus proper has preponderately spiral 

 sculpture sometimes varied by rude axial nodes or projecting lamellae, 

 the shell substance tending to have a translucent outer layer and the 

 3343— 19— Proe.N.M. vol.54 15 



