CHAP. III. THE GASSING, OR HELMETS. 65 



The type of Muricidea, is the harp-like Mureoc Magel- 

 lanicus* Where, as in very many other of the small 

 murexes, the progressive growth of the shell is marked 

 by longitudinal ridges, either foliated or spined, some- 

 times as close together, and nearly as regular, as those 

 upon the harp-shells. The outer lip is quite smooth, 

 and the inner Hp thin : there is no internal groove ; and 

 the basal canal is almost always closed over, so as to 

 form an internal tube, open only at the two ends. The 

 connection of this group of Murices to the true genus 

 Murex is so close, that they have never, until now, been 

 separated ; so that, being connected to Triton by means 

 of Vitulina, also a Lamarckian murex, we find the whole 

 forming a circular group of themselves. 



(57.) Ill the Cassin.e, or helmet-shells, the first cha- 

 racter which strikes us is their large and often gigantic 

 size : the spire is remarkably short; and the base, instead 

 of being prolonged, as in the Muricince, is either truncated 

 so as merely to present a wide notch, or is very short, 

 and turned back on the body-whorl. These are the 

 typical characters of the sub- family, but much remains 

 to designate the genera. Our attention has been more 

 especially called to this group, not merely from^ the size 

 and beauty of the shells, but from the great reluctance 

 some conchologists have manifested to adopt the genus 

 CyprcEcassis, proposed by j\Ir. Stuchbury, whose valuable 

 Essay upon the growth of corals has rendered his 

 name familiar to naturalists. That Cyprcecassis pos- 

 sessed a decided relation, either by affinity or analogy, 

 to Cyprcea, we had long been persuaded. But vre 

 freely confess, that previous to, and even for some time 

 after, its being proposed as a genus, we looked upon it 

 only as a subordinate type of Cassis. Anxious, never- 

 theless, to arrive at some definite conclusion on this 

 point, we were induced to re-examine the whole of the 

 Lamarckian genus Cassis; the result of which has con- 

 vinced us that our first impression was erroneous, and 

 that Cyprcecassis is as truly a natural genus as any in 



* Ency. Method, pi. 414. fig. 4. a, b. 

 F 



