English: Illustrated Index of British Shells. Plate XX.
Fig. Name in text Accepted name (2013)
1 Tornatella fasciata Lamarck Acteon tornatilis
2 Ovula patula Pennant Xandarovula patula
3 Ovula acuminata Bruguière Volvulella acuminata
4 Cylichna cylindracea Pennant Cylichna cylindracea
5 Cylichna obtusa Montagu Retusa obtusa
6 Cylichna mamillata Philippi Retusa mammillata
7 Cylichna truncata Adams Retusa truncatula
8 Cylichna nitidula Lovén Cylichnina nitidula
9 Cylichna conulus Deshayes not matched
10 Cylichna strigilla Lovén not matched
11 Cylichna umbilicata Montagu Cylichnina umbilicata
12, 13 Cylichna Lajonkaireana Basterot Retusa obtusa
14 Amphispira hyalina Turton Diaphana minuta
15 Amphispira globosa Jeffreys not matched
16 Akera bullata Müller Akera bullata
17 Bulla Cranchii Leach Roxania utriculus
18 Bulla cornea Lamarck Haminoea hydatis
19 Bulla hydatis Linnaeus Haminoea hydatis
20 Philine aperta Linnaeus Philine aperta
21 Philine scabra Müller Philine scabra
22 Philine quadrata S. Wood Philine quadrata
23 Philine catena Montagu Philine catena
24 Philine punctata Clark Philine punctata
25 Philine pruinosa Clark Philine pruinosa
26 Scaphander lignarius Linnaeus Scaphander lignarius
27 Scaphander zonatus Turton Scaphander lignarius
28 Aplysia hybrida Sowerby Aplysia punctata
29 Pleurobranchus membranaceus Montagu Pleurobranchus membranaceus
30 Pleurobranchus plumula Montagu Berthella plumula
31 Spirula Peronii Spirula spirula
Date 1859
Source http://archive.org/details/illustratedindex00sowe
Accepted names from WoRMS database and Marine Species Identification Portal
Author George Brettingham Sowerby II (1812–1884)
Source: https://commons.wikimedia.org/wiki/File:Illustrated_Index_of_British_Shells_Plate_20.jpg

The ram's horn squid, little post horn squid or tail-light squid (Spirula spirula) is a species of deep-water squid-like cephalopod mollusk. It is a deep-ocean dweller. The shell of Spirula is extremely light in weight, very buoyant, and surprisingly durable; it very commonly floats ashore onto tropical beaches all over the world. This seashell is known to shell collectors as the ram's horn shell or simply as Spirula.