MUSEUM OF COMPARATIVE ZOOLOGY. 341 



lip, and a less prominent broad spiral between the last and the columella, 

 which does not appear inside the peristome; these are crossed by, on the last 

 whorl, about thirty strong narrow equal regularly-spaced cord-like riblets 

 which are hardly nodulous at the intersections; the interstices are deep, and 

 narrower spirally than they are axially; whorls moderately rounded and 

 well marked; aperture rounded, waved externally by the sculpture, internally 

 lirate; pillar concave, callous; a callus connecting it with the outer lip; base 

 rounded, strongly sculptured, the aperture slightly varicose, but in older speci- 

 mens than those before me probably markedly so. Max. Ion. of shell, 6.0; 

 of last whorl, 3.0; max. lat. of shell, 2.5 mm. 



Habitat. Off Cape Hatteras, in 63 fms., sand, at U. S. Fish Commission 

 Station 2595, bottom temperature 75°. 



Florida, at Marco, No Name Key, and Key West, on grassy bottom, between 

 low water and two fathoms, H. Hemphill. 



This very lovely latticed little shell is shorter and more Odostomia-like than 

 the preceding species. The sculpture is a good deal like that of Mathilda 

 Rushii, but less crowded and less sharp. The specimens were all slightly less 

 than adult, and the varicosity of the outer lip would doubtless have increased 

 if they had continued to grow. 



Order SCUTIBRANCHIATA. 



Suborder RHIPHIDOGLOSSA. 



Super-Family SCHISMATOBRANCHIA. 



This group, like its compeer, the Dicranobranchia of Gray, to use the oldest 

 of their numerous appellations, may be divided into two sections, one contain- 

 ing spiral shells, and the other subcorneal or uncoiled species. Two of the 

 four sections referred to will possess forms provided with an intromittent male 

 organ, and others destitute of such an organ. The spiral Schismatobranchs 

 are generally without a verge; Neritina and Helicina were until lately the 

 known exceptions. Turcicula Bairdii, Margarita infundibulum, and several 

 allied forms, are now added to the list. M. infundibulum has also a remark- 

 able tubular modification of the right anterior epipodial lappet, so that it 

 serves as a conduit for the seminal product, from the short tubular verge to its 

 destination. The conical or limpet-like Dicranobranchs are usually without 

 a verge, but it is present in Cranopsis, and probably in other genera. So far, 

 no spiral Dicranobranch is known to have a verge, and no limpet-like Schis- 

 matobranch to be without one. But our ignorance of the majority of forms is 

 so great that no one can say how long the negative evidence will have any 

 value. It is only within a few years that the writer has been enabled to deter- 

 mine these facts, which seem so opposed to our previous experience and sys- 

 tematic definitions. The need of investigation and the field for it, in the 



