18S4. 



PROCEEDINGS OF THE NATIONAL MUSEUM. 167 



evidently very abundant at these islands. In the younger or smaller 

 specimens there is a tendency to a serial or alternate arrangement of 

 prominent libs with finer intermediate ones or riblets, as Carpenter 

 terms them in his reference to this species in the Mazatlan catalogue, 

 page 132, species 139.* The synonymy as above given is not 

 complete; it should include other specific and varietal names ; as the 

 literature is not accessible by which I can verify the references and 

 alhisions to many s])ecies made by Carpenter and other authors whose 

 comments I have read, I prefer to submit the above with my own notes 

 and observations. 



The variety ^a/ma^ft (No.0031>(i, IT.S.N.M.) is simply a flattened form of 

 lecanium occasionally'met with. I regard tt'^w/mr^a as a less strongly 

 sculptured and a closely ribbed \ariety oi lecanium minus intermediate 

 riblets, or with smooth interspaces where riblets occur in typical 

 lecanium. 



The number of species and varieties which have been made is owing 

 apparently to the excessive variability in the number of riblets as 

 w^ell as to the varying pronunence of the same, also to variation in ele- 

 vation or depression. Some individuals have 50 or more closely set 

 nearly equal ribs, as do some of my largest specimens which measure 

 1.03 greatest length with an elevation of .55 inch; examples of these 

 would be regarded as Carpenter's wqnllirata (No. 60395, U. S. N. M.). 

 Sometimes as many as GO nearly ecjual ribs are exhibited in specimens 

 only .(>9 inch in length, and .29 inch elevation. In these closely and 

 ecjually ribbed individuals nearly or ({uite all of the ribs commence or 

 start at the apex, are present in the adolescent shell, and are developed 

 and maintained or continued with the growth of the shell through to 

 maturity. 



There is also a rather rare flattened intermediate form between those 

 just descril>ed and the common coarsely ribbed ones, Avhich connects 

 the two, that is to say, the a'tinillratc variety with tlie typical lecanium, 

 which has 30 to 40 nearly or quite equal ribs with only occasional 

 inconspicuous inter-ribs or lira-; this variety ])robably Carpenter was 

 not familiar with, as it is not common. 



In the typical lecanium, which is, so far as my observation goes, the 

 most abundant in individuals, the prominent ribs vary in number from 

 as few as 11 in young shells to 23 or more in adults, the interspaces 

 being filled with tine stria*; it is often the case tliat the number of the 

 coarse ribs in the same individual, in its earlier stages of growth, is 

 less than the adult shell exhibits, as the coarse ribs often bifurcate at 

 some incremental stage and continue, each part being of equal promi- 

 nence with the main rib from w^hich they forked or branched. Such 

 instances of lecanium as exhibit the fewest ribs, when flattened make 



"Mr. Fisher's specimens, though numerous, were, as ii whole, rather small ; a lot of 

 about 70 not exceeding an average of .49 inch in length. 



