Bernard and others. Some, as Kingsley, have placed the Merostomata next to the Arachnida and united the two in one class. The scheme proposed by Kingsley [1894, p. 122] is as follows:
| Phylum, Arthropoda |
| Subphylum I, Branchiata |
| Class I, Crustacea |
| Subclass 1, Trilobitae |
| Subclass 2, Eucrustaceae |
| Class II, Acerata |
| Subclass 1, Gigantostraca (Merostomata) |
| Subclass 2, Arachnida |
| Subphylum II, Insecta |
Lankester, in his paper "Limulus an Arachnid?" and his followers have gone farther and placed the Merostomata under the class Arachnida. They propose the following classification [see Shipley, 1909, p. 258]:
| Class, Arachnida |
| Subclass 1, Delobranchiata (Merostomata) |
| Order (I), Xiphosura |
| Order (II), Eurypterida |
| Subclass 2, Embolobranchiata |
| Order (I), Scorpionidae |
| Order (II), Pedipalpi |
| etc. |
The Delobranchiata, which term is equivalent to Dana's Merostomata, are characterized by their gills which are patent and exposed; the Embolobranchiata have lungbooks or tracheae. We prefer to retain the term Merostomata, there being no apparent need for a new word.
As there is a burning interest attaching to the question whether we should regard the merostomes of the Siluric as giant marine arachnids or archaic crustaceans, we here briefly review the arguments for the relationship of the merostomes with the scorpions; and since, the larval
