The sentence beginning verse 19, “Ammon answered and said unto him”, could be missing an initial and. Elsewhere in the Book of Mormon text, narrative uses of “X answereth/answered” are almost always connected to the previous text by and (15 times). There is only one case where the connective element is something other than and; in that one case, the connective element is now followed by a subordinate clause:
So the use here in Alma 18:18 of “X answereth/answered” without any connective element is quite unique for the Book of Mormon. Even so, the and is not required, as can be seen from narrative uses of “X saith/said” in the text. In almost every case, there is a connective element, usually and, before “X saith/said”; yet there are two instances of “X saith/said” without any connective element:
These examples suggest that not only can “X saith/said” begin a sentence in discourse narratives, but so can “X answereth/answered”. Note further that in all three examples without a connecting and, the subject is a name rather than a pronoun (thus Moroni in Alma 46:23 and Ammon here in Alma 18:19 as well as in Alma 18:34). In other words, there may be a tendency for the connective and to be lacking when the sentence begins with a name rather than with a pronoun. The critical text will therefore leave the unique instance here in Alma 18:19 of “X answereth/answered” without any and (or any other connective element).
In this regard, biblical usage in the King James Bible is more mixed than Book of Mormon usage. Consider, for instance, the conjoined predicate “answered and said”. In the Old Testament, “answered and said” almost always has and or some other connector (such as then, but, or furthermore) in front of the subject. The only exceptions are ten occurrences in the book of Daniel, as in “the king answered and said” (Daniel 2:8). In the New Testament, usage is basically evenly divided between having some connector (and, but, or then) versus none (52 to 43). Thus the current text for Alma 18:19 without any and preceding “Ammon answered” is quite acceptable in terms of King James language.
Summary: Accept in Alma 18:19 the occurrence of “Ammon answered and said” without any connecting and between it and the preceding narrative.