262 BULLETIN OF THE 



This is the species forming the so-called " wormrock " of West Florida, or at 

 least all of the "wormrock" which I actually examined. It would seem to 

 belong in the same group with V. lambricalis, but I'onns much more compact 

 masses, with the upper portions of the tubes parallel to each other and erect, 

 close together, recalling TubuUpora. It forms masses which are really as dan- 

 gerous as coral reefs to boats navigating the shallow water in which they flour- 

 ish. I observed patches of twenty or thirty feet radius, with the top nearly 

 level and barely dry at ordinary low water. The same species is found in 

 deeper water, but there it is not combined in large colonies, but is clustered in 

 small bunches on stones and shells. The young is sculi)tured in a way very 

 similar to the two species of Orbigny above cited, and with which it has been 

 erroneously combined. Both these belong to the group with strong internal 

 laminae; on the otlier hand, the present species is apparently without lamina). 



I ha\e Petaloconchus irregularis Orbigny, from 27 fnis., sand, between the Mis- 

 sissippi delta and Cedar Keys, Florida. It is more prone than our species, the 

 laminae are extremely prominent except near the aperture, and there are three 

 of them. I do not believe it ever stands erect in large masses so as to form 

 "rock" comparable to that of V. nigricans, but I have found specimens en- 

 tangled with the V. nigricans in the small scattered bunches. The variations 

 in this group are immense. Many hundred specimens of V. nigricans which 

 I have examined are totally devoid of laminae; in a few, which in their en- 

 tanglement I cannot distinguish from the others (though they mat/ be distinct), 

 I have thought I saw traces, near the apex, of a faint median ridge. However 

 this may be, it is just as well to have a specific name undeniably applicable 

 to our Floridian shell, and the others are in such a confused state that they 

 cannot be safely used. Of course, if it should prove that the faint lamina 

 mentioned is normally present in this species, and is of systematic importance, 

 V. nigricans would have to be referred to Vermetus proper, as used by Try on 

 and Fischer. 



Genus VERMETUS (Adaxson) Morch. 



Subgenus PETALOCONCHUS Lea. 

 Vermetus (Petaloconchus) erectus Dall. 



Plate XXXVIII. Fig. 4. 



Vermetus erectus Dall, in Agassiz, Three Cruises of the Blake, II. p. 71, fig. 297, 



1888. 



Nucleus smooth, milk-white, polished, bulimoid, two-whorled ; when the 

 irregular growth commences the nucleus may be turned upside down or take 

 almost any other position, most appear to lie on their sides. Early part of the 

 shell prone, irregularly contorted; as the whorls lie, the normal sculpture 

 appears to be a single minutely undulated longitudinal ridge on the middle of 



