Gasteropoda. ]^22 Patella. 



Patella, Linn. 1758. 



angulosa, Gein. (Helcion), Nacht. Kreid. 11, 6, 2-4. 

 camjmnulata, Reuss (Helcion), Bohm. Kreid. 110, 44, 9. 

 comosa, Roem. (Emarginula), Nord. Kreid. 77, 11, 2. 

 corrugata, Forbes (Helcion), G. T. vol. vii, 137, 12, 11. 

 elevata, Forbes (H. Reussii), G. T. vol. vii, pi. 12, f. 10. 

 laevis, Sow. (Helcion), M. Con. pi. 139, 3, 4. 

 lamellosa, Koch. (Helcion), Beitr. Zurkenn. Ool. 51, 6, 4. 

 orbis, Roem. (Helcion), Nord. Kreid. pi. 11, f. 1. 

 quadrata, Koch. (H. subquadrata), Beitr. Ool. 51, G, 3. 

 semistriata, Munst. (Helcion), in Goldf. 7, 1G7, 12. 

 tentorium, Morton (Helcion), Synopsis, 50, 1, 11. 



Pedipes, Adanson, 1757. 



incrassata, Mant. Sp. (Avellana), Quenst. Wiegman's Ar- 

 chiv. 3, 249. 



PERISSOLAX, Gabb, 1861.=*^ 



?brevissinia, d'Orb. Sp. (Fusus), Gabb, 18G1. Ala. C, 



* It is with considerable reluctance that I propose a new genus in this family ; 

 but I am obliged either to do so, or suggest a modification of the characters of 

 the genus Fusus as now understood. There exists a group of shells in the creta- 

 ceous formation, of which Fusus longirostris, and F. trivolvas, may be taken as 

 the types. The species of this group have been referred to various genera, but 

 they all agree in possessing the general characters of Fusus, but with a very low 

 spire, patulous body, whorl, and long, straight, slender canal ; in short, they have 

 nearly the form of the genus Tudicla or Haustellum, but have no folds, plates, or 

 teeth on the columella. I have never seen the outer lip, but judging from cast.^s 

 and figures, I believe it to be plain. These shells cannot be referred to Tudicla, 

 Fasciolauia, or Busvcon, because of the plain columella. The spire is very low, 

 and as now understood the spire of Fusus is as long as the aperture. They resemble 

 the genus Papillina, Conrad, of which P. papillata, Con. {Fusus id.) is the 

 type, but that genus has a fold on the columella like BusvcON. Pvrula is un- 

 tenable ; the umbilicus being entirely absent they cannot be referred to Rapa, 

 even were the canal short. In view of these considerations, I propose the gene- 

 ric name Perissolax {ircpia-a-og, excessive, and wAa^, furrow or canal), prefer- 

 ring to separate the species from Fusus, rather than dispute the high authority 

 of H. and A. Adams, and others, who maintain that the length of the spire in 

 that genus is of generic value. 



This genus seems to be peculiar to the upper member.^; of the cretaceous forma- 

 tion, unless the recept species, Fijrula coarctata. Sow., may prove to belong to 



